System and method for reducing halogen levels necessary for mercury control, increasing the service life and/or catalytic activity of an scr catalyst and/or control of multiple emissions

ABSTRACT

The present invention relates generally to the field of emission control equipment for boilers, heaters, kilns, or other flue gas-, or combustion gas-, generating devices (e.g., those located at power plants, processing plants, etc.) and, in particular to a new and useful method and apparatus for: (i) reducing halogen levels necessary to affect gas-phase mercury control; (ii) reducing or preventing the poisoning and/or contamination of an SCR catalyst; and/or (iii) controlling various emissions. In still another embodiment, the present invention relates to a method and apparatus for: (A) simultaneously reducing halogen levels necessary to affect gas-phase mercury control while achieving a reduction in the emission of mercury; and/or (B) reducing the amount of selenium contained in and/or emitted by one or more pieces of emission control equipment for boilers, heaters, kilns, or other flue gas-, or combustion gas-, generating devices (e.g., those located at power plants, processing plants, etc.).

RELATED APPLICATION DATA

This patent application claims priority to and is a continuation-in-partof U.S. patent application Ser. No. 13/769,686 filed Feb. 18, 2013 andtitled “System and Method for Increasing the Service Life and/orCatalytic Activity of an SCR Catalyst and Control of MultipleEmissions,” which itself claims priority to and is acontinuation-in-part of U.S. patent application Ser. No. 13/117,332filed May 27, 2011 and titled “System and Method for Increasing theService Life and/or Catalytic Activity of an SCR Catalyst and Control ofMultiple Emissions,” which itself claims priority to and is acontinuation-in-part of U.S. patent application Ser. No. 12/691,527filed Jan. 21, 2010 and titled “System and Method for Protection of SCRCatalyst and Control of Multiple Emissions,” which itself claimspriority to and is a non-provisional of U.S. Provisional PatentApplication No. 61/171,619 filed Apr. 22, 2009 and titled “System andMethod for Protection of SCR Catalyst.” The complete text of thesepatent applications are hereby incorporated by reference as though fullyset forth herein in their entireties.

FIELD AND BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of emission controlequipment for boilers, heaters, kilns, or other flue gas-, or combustiongas-, generating devices (e.g., those located at power plants,processing plants, etc.) and, in particular to a new and useful methodand apparatus for: (i) reducing halogen levels necessary to affectgas-phase mercury control; (ii) reducing or preventing the poisoningand/or contamination of an SCR catalyst; and/or (iii) controllingvarious emissions. In another embodiment, the method and apparatus ofthe present invention is designed to: (a) achieve a reduction in thelevel of one or more halogens, or halogen-containing compounds,necessary to affect gas-phase mercury control; (ii) achieve protectionof, increase the catalytic activity, and/or increase the catalytic lifespan of an SCR catalyst; and/or (iii) achieve control of variousemissions from a combustion process (e.g., control of seleniumemissions). In still another embodiment, the present invention relatesto a method and apparatus for: (A) simultaneously reducing halogenlevels necessary to affect gas-phase mercury control while achieving areduction in the emission of mercury; and/or (B) reducing the amount ofselenium contained in and/or emitted by one or more pieces of emissioncontrol equipment for boilers, heaters, kilns, or other flue gas-, orcombustion gas-, generating devices (e.g., those located at powerplants, processing plants, etc.).

2. Description of the Related Art

NO_(x) refers to the cumulative emissions of nitric oxide (NO), nitrogendioxide (NO₂) and trace quantities of other nitrogen oxide speciesgenerated during combustion. Combustion of any fossil fuel generatessome level of NO_(x) due to high temperatures and the availability ofoxygen and nitrogen from both the air and fuel. NO_(x) emissions may becontrolled using low NO_(x) combustion technology and post-combustiontechniques. One such post-combustion technique involves selectivecatalytic reduction (SCR) systems in which a catalyst facilitates achemical reaction between NO_(x) and a reagent (usually ammonia) toproduce molecular nitrogen and water vapor.

SCR technology is used worldwide to control NO_(x) emissions fromcombustion sources. This technology has been used widely in Japan forNO_(x) control from utility boilers since the late 1970's, in Germanysince the late 1980′s, and in the US since the 1990's. Industrial scaleSCRs have been designed to operate principally in the temperature rangeof 500° F. to 900° F., but most often in the range of 550° F. to 750° F.SCRs are typically designed to meet a specified NO_(x) reductionefficiency at a maximum allowable ammonia slip. Ammonia slip is theconcentration, expressed in parts per million by volume, of unreactedammonia exiting the SCR.

For additional details concerning NO removal technologies used in theindustrial and power generation industries, the reader is referred toSteam/its generation and use, 41^(st) Edition, Kitto and Stultz, Eds.,Copyright 2005, The Babcock & Wilcox Company, Barberton, Ohio, U.S.A.,particularly Chapter 34—Nitrogen Oxides Control, the complete text ofwhich is hereby incorporated by reference as though fully set forthherein.

Regulations issued by the EPA promise to increase the portion of utilityboilers equipped with SCRs. SCRs are generally designed for a maximumefficiency of about 90 percent. This limit is not set by any theoreticallimits on the capability of SCRs to achieve higher levels of NOdestruction. Rather, it is a practical limit set to prevent excessivelevels of ammonia slip. This problem is explained as follows.

In an SCR, ammonia reacts with NO according to one or more of thefollowing stoichiometric reactions (a) to (d):

4NO+4NH₃+O₂→4N₂+6H₂O   (a)

12NO₂+12NH₃→12N₂+18H₂O+3O₂   (b)

2NO₂+4NH₃+O₂→3N₂+6H₂O   (c)

NO+NO₂+2NH₃→2N₂+3H₂O   (d).

The above catalysis reactions occur using a suitable catalyst. Suitablecatalysts are discussed in, for example, U.S. Pat. Nos. 5,540,897;5,567,394; and 5,585,081 to Chu et al., all of which are herebyincorporated by reference as though fully set forth herein. Catalystformulations generally fall into one of three categories: base metal,zeolite and precious metal.

Base metal catalysts use titanium oxide with small amounts of vanadium,molybdenum, tungsten or a combination of several other active chemicalagents. The base metal catalysts are selective and operate in thespecified temperature range. The major drawback of the base metalcatalyst is its potential to oxidize SO₂ to SO₃; the degree of oxidationvaries based on catalyst chemical formulation. The quantities of SO₃which are formed can react with the ammonia carryover to form variousammonium-sulfate salts.

Zeolite catalysts are aluminosilicate materials which function similarlyto base metal catalysts. One potential advantage of zeolite catalysts istheir higher operating temperature of about 970° F. (521° C.). Thesecatalysts can also oxidize SO₂ to SO₃ and must be carefully matched tothe flue gas conditions.

Precious metal catalysts are generally manufactured from platinum andrhodium. Precious metal catalysts also require careful consideration offlue gas constituents and operating temperatures. While effective inreducing NO_(x), these catalysts can also act as oxidizing catalysts,converting CO to CO₂ under proper temperature conditions. However, SO₂oxidation to SO₃ and high material costs often make precious metalcatalysts less attractive.

As is known to those of skill in the art, various SCR catalysts undergopoisoning when they become contaminated by various compounds including,but not limited to, certain phosphorus compounds such as phosphorusoxide (PO) or phosphorus pentoxide (P₂O₅). Additionally, it is also wellknown that SCR catalysts degrade over time and have to be replacedperiodically at a significant cost and loss of generating capacity. In atypical 100 MWe coal plant the downtime and cost associated with thereplacement of underperforming catalyst can be in the neighborhood ofone million US dollars or more.

More particularly, as the SCR catalysts are exposed to the dust ladenflue gas there are numerous mechanisms including blinding, masking andpoisoning that deactivates the catalyst and causes a decrease in thecatalyst's performance over time. The most common catalyst poisonencountered when burning eastern domestic coal (i.e., coal mined in theeastern United States) is arsenic. The most common catalyst poisonencountered when burning western domestic coal (i.e., coal mined in thewestern United States) is phosphorus and calcium sulfate is the mostcommon masking mechanism. One method of recycling the used catalyst isthe process called regeneration washing or rejuvenation. The initialsteps of the regeneration process involve the removal of these toxicchemicals by processing the catalysts through various chemical baths inwhich the poisons are soluble. While this treatment process does anexcellent job of removing the desired poisons it produces wastewaterwith very high arsenic concentrations.

In another situation, Powder River Basin/Lignite coal plants, anycoal/biomass co-combustion, or any coal/bone meal co-combustion or evenpure biomass combustion power plants will suffer from phosphoruscontamination of their SCR catalysts.

Additionally, beyond controlling NO_(x) emissions, other emissioncontrols must be considered and/or met in order to comply with variousstate, EPA and/or Clean Air Act regulations. Some other emissioncontrols which need to be considered for boilers, heaters, kilns, orother flue gas-, or combustion gas-, generating devices (e.g., thoselocated at power plants, processing plants, etc.) include, but are notlimited to, mercury, SO_(x), and certain particulates.

Furthermore, in most situations, if not all, it is desirable to removevarious SO_(x) compounds by way of either one or more wet flue gasdesulfurization (WFGD) units or one or more dry flue gas desulfurization(DFGD) units from a flue gas. As is known to those of skill in the art,in conjunction with SO_(x) removal it is common (and now required inmost instances) to also remove and/or reduce the amount of mercury in aflue gas. One suitable method of mercury control is mercury oxidationand capture via the use of one or more halogen compounds to accomplishthe aforesaid mercury oxidation and the subsequently capturing theoxidized mercury compound (e.g., in the form of a mercuric halide). Ithas been found that when mercury control is accomplished in whole, or inpart, through the use of one or more halogen compounds (e.g., halidesalts such as calcium bromide, etc.) that such compounds negativelyimpact on the selenium speciation in the flue gas which in turnnegatively impacts the amount of selenium that is emitted via the liquideffluent outflow from one or more WFGD units, and or the particulatematter produced by one or more DFGD units that are utilized to controlSO_(x) in the same flue gas stream. However, it should be noted that thepresent invention is not limited to just the aforementioned situation.In fact, in one embodiment the present invention relates to a method andapparatus for controlling, mitigating and/or reducing the amount ofselenium contained in and/or emitted by one or more pieces of emissioncontrol equipment for boilers, heaters, kilns, or other flue gas-, orcombustion gas-, generating devices (e.g., those located at powerplants, processing plants, etc.). In another embodiment, the presentinvention relates to method and apparatus for controlling the seleniumspeciation in one, or both, of a gas phase or a aqueous phase by theaddition of at least one metal additive at any point upstream (as willbe detailed below) of either a wet flue gas desulfurization (WFGD) unitand/or a dry flue gas desulfurization (DFGD) unit. In still anotherembodiment, present invention offers a method and apparatus by which tosimultaneously control at least selenium speciation in one, or both, ofa gas phase or an aqueous phase while further controlling at least oneof gas phase phosphorus, gas phase sodium, gas phase potassium, and/ormercury in at least one emission from a combustion process.

In, for example, a coal combustion process the addition of one or morehalogens, or halogen-containing compounds, (e.g., calcium bromide, orany other suitable bromine-containing compound) forms one or morecorresponding gaseous hydrogen halide compounds (e.g., HBr, HCl, HF,and/or Hl). Hydrogen halide gases including, but not limited to, HBr gasare not very reactive towards mercury and cause both high temperaturecorrosion under reducing atmosphere in a furnace and low temperaturecorrosion at an air heater outlet. For example, HBr is converted to Brand Br₂ gas by the Deacon reaction shown below:

4HBr(g)+O₂(g)→2H₂O(g)+2Br₂  (g).

Br₂, or another elemental form of a different halogen, in the gas phasethen reacts with Hg in the gas phase to produce, for example, mercuricbromide (HgBr₂) in the gas phase. Mercuric bromide is the compound inthis example that contains the oxidized mercury. This form of mercury iseasily removed using flue gas desulfurization (FGD) equipment.Additionally, other coal-based process such as the production of syngasfrom coal produce undesirable levels of phosphorus compounds therebyresulting in the undesirable deactivation of one or more catalystsassociated with such production processes.

Given the above, a need exists for a method that provides for anyeconomical and environmentally suitable method and/or system thatpermits: (i) a reduction in the halogen levels necessary to affectgas-phase mercury control; (ii) a reduction in, or prevention of, thepoisoning and/or contamination of an SCR catalyst; and/or (iii) thecontrol of various emissions. In another instance, there exists a needto control selenium emission from one or more pieces of emission controlequipment that are used in conjunction with a combustion process.Additionally, or alternatively, a need exists for a method to controlselenium emission while simultaneously increase catalytic life spanand/or catalytic activity of an SCR catalyst via the control of one ormore gas phase compounds such as phosphorus, sodium, and/or potassium,and even in some instances the further ability to control mercuryemission.

SUMMARY OF THE INVENTION

The present invention relates generally to the field of emission controlequipment for boilers, heaters, kilns, or other flue gas-, or combustiongas-, generating devices (e.g., those located at power plants,processing plants, etc.) and, in particular to a new and useful methodand apparatus for: (i) reducing halogen levels necessary to affectgas-phase mercury control; (ii) reducing or preventing the poisoningand/or contamination of an SCR catalyst; and/or (iii) controllingvarious emissions. In another embodiment, the method and apparatus ofthe present invention is designed to: (a) achieve a reduction in thelevel of one or more halogens, or halogen-containing compounds,necessary to affect gas-phase mercury control; (ii) achieve protectionof, increase the catalytic activity, and/or increase the catalytic lifespan of an SCR catalyst; and/or (iii) achieve control of variousemissions from a combustion process (e.g., control of seleniumemissions). In still another embodiment, the present invention relatesto a method and apparatus for: (A) simultaneously reducing halogenlevels necessary to affect gas-phase mercury control while achieving areduction in the emission of mercury; and/or (B) reducing the amount ofselenium contained in and/or emitted by one or more pieces of emissioncontrol equipment for boilers, heaters, kilns, or other flue gas-, orcombustion gas-, generating devices (e.g., those located at powerplants, processing plants, etc.).

Accordingly, one aspect of the present invention is drawn to a methodfor reducing the amount and/or concentration of one or morehalogen-containing compounds used to achieve mercury capture in a fluegas, the method comprising the steps of: (a) providing one or morehalogen-containing compounds to a combustion zone or flue gas stream ofa furnace, or boiler, prior to entry of the flue gas into an SCR,wherein the halogen portion of the one or more halogen-containingcompounds are liberated in the combustion zone or flue gas stream of thefurnace or boiler and are converted to one or more corresponding gaseoushydrogen halide compounds; (b) providing one or more metal-bearingcompounds to a combustion zone or flue gas stream of a furnace, orboiler, at a point that is both prior to entry of the flue gas into anSCR as well as after a point that where the majority of the one or morehalogen-bearing compounds have been converted to the correspondinggaseous hydrogen halides; (c) permitting one or more metal-bearingcompounds to catalyze the conversion of the corresponding one or morehydrogen halides to one or more corresponding elemental halogencompounds; and (d) permitting the resulting one or more correspondingelemental halogen compounds to react with gaseous mercury present in thecombustion zone or flue gas stream of the furnace, or boiler, therebyresulting in oxidation of the gaseous mercury so as to convert thegaseous mercury into one or more corresponding mercury halides.

In yet another aspect of the present invention, there is provided amethod for reducing the amount and/or concentration of one or moregaseous acid compounds in a flue gas, the method comprising the stepsof: (i) providing at least one fossil fuel, or biomass, to a furnace, orboiler; (ii) combusting the at least one fossil fuel, or biomass,wherein the combustion process produces one or more gaseous acidcompounds; (iii) providing one or more metal-bearing compounds to acombustion zone or flue gas stream of the furnace, or boiler; (iv)permitting one or more metal-bearing compounds to react with the one ormore gaseous acid compounds present in the combustion, or flue, gas inorder to convert the one or more gaseous acid compounds into a lessacidic metal-containing compound.

In yet another aspect of the present invention, there is provided amethod for reducing the concentration of one or more gaseous phosphoruscompounds in a syngas production process, the method comprising thesteps of: (A) providing at least one fossil fuel, or biomass, to asyngas reactor; (B) providing one or more metal-bearing compounds to thesyngas reactor; (C) reacting the at least one fossil fuel, or biomass,and the one or more metal-bearing compounds to produce a syngas, whereinthe syngas has a reduced level of one or more one or more gaseousphosphorus compounds as compared to the amount and/or concentration ofone or more gaseous phosphorus compounds present in a syngas productionprocess that does not utilize the one or more metal-bearing compounds.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific benefits attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich exemplary embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a typical fossil fuel burningfacility with an SCR system, and which includes a system for practicingthe methods of the present invention; and

FIG. 2 is a graph illustrating one example of an increase in catalyticactivity and/or catalytic lifespan as realized via utilization of asystem and method in accordance with one embodiment of the presentinvention.

DESCRIPTION OF THE INVENTION

The present invention relates generally to the field of emission controlequipment for boilers, heaters, kilns, or other flue gas-, or combustiongas-, generating devices (e.g., those located at power plants,processing plants, etc.) and, in particular to a new and useful methodand apparatus for: (i) reducing halogen levels necessary to affectgas-phase mercury control; (ii) reducing or preventing the poisoningand/or contamination of an SCR catalyst; and/or (iii) controllingvarious emissions. In another embodiment, the method and apparatus ofthe present invention is designed to: (a) achieve a reduction in thelevel of one or more halogens, or halogen-containing compounds,necessary to affect gas-phase mercury control; (ii) achieve protectionof, increase the catalytic activity, and/or increase the catalytic lifespan of an SCR catalyst; and/or (iii) achieve control of variousemissions from a combustion process (e.g., control of seleniumemissions). In still another embodiment, the present invention relatesto a method and apparatus for: (A) simultaneously reducing halogenlevels necessary to affect gas-phase mercury control while achieving areduction in the emission of mercury; and/or (B) reducing the amount ofselenium contained in and/or emitted by one or more pieces of emissioncontrol equipment for boilers, heaters, kilns, or other flue gas-, orcombustion gas-, generating devices (e.g., those located at powerplants, processing plants, etc.).

As used herein, “majority” means any amount in excess of 50 weightpercent. Also as used herein, “less acidic metal-containing compound”means any metal-containing compound that contains at least onenon-hydrogen portion of an acid compound (e.g., HBr, HCl, HF, Hl, H₃PO₄,etc.) and has a pH less than that of such related acid compound such.

While the present invention will be described in terms of SCR systemswhich use ammonia as the NO_(x) reducing agent, since ammonia isfrequently preferred for economic reasons, the present invention is notlimited to ammonia based systems. The concepts of the present inventioncan be used in any system which uses an ammoniacal compound. As used inthe present disclosure, an ammoniacal compound is a term meant toinclude compounds such as urea, ammonium sulfate, cyanuric acid, andorganic amines as well as ammonia (NH₃). These compounds could be usedas reducing agents in addition to ammonia, but as mentioned above,ammonia is frequently preferred for economic reasons. Somenon-ammoniacal compounds such as carbon monoxide or methane can be usedas well, but with loss in effectiveness.

Furthermore, although the present invention is described in terms of amercury oxidation and capture method that utilizes a halogen compoundthat is in the form a halide salt (e.g., calcium bromide), the presentinvention is not limited to just this type of mercury oxidation andcapture. Rather, any type of halogen-based mercury control method can beutilized in conjunction with the present invention as the presentinvention. In some embodiments, the present invention as the presentinvention also seeks to control simultaneously one or more of the amountand/or concentration of: (i) gas phase phosphorus and/or (ii) thenature, or type, of the selenium speciation. In other embodiments, thepresent invention seeks to control simultaneously the amount and/orconcentration of gas phase phosphorus, the amount and/or concentrationof one or more halogen compounds necessary for mercury control, and/orand the nature of the selenium speciation in a flue gas.

Although the present invention is described in relation to a boiler, ora fossil fuel boiler, it is not limited solely thereto. Instead, thepresent invention can be applied to any combustion source that generatesNO_(x) regardless of whether such a combustion source is utilized inconjunction with a boiler, or a steam generator. For example, thepresent invention could be used in combination with a kiln, a heater, orany other type of combustion process that generates, in whole or inpart, a flue gas or combustion gas containing NO_(x). Accordingly, thedescription below is to be construed as merely exemplary.

As illustrated in FIG. 1, the present invention may be applied to aboiler installation which employs a wet flue gas desulfurization (WFGDor wet scrubber) for removal of sulfur oxides from the flue gases, asshown in the upper right-hand side of FIG. 1. In this configuration, thewet scrubber is typically preceded (with respect to a direction of fluegas flow through the system) by a particulate collection device (PCD),advantageously a fabric filter (FF) bag house, or an electrostaticprecipitator (ESP). If desired, there may also be provided a wetelectrostatic precipitator (wet ESP or WESP) which may be provided as afinal “polishing” stage for fine particulate or SO₃. Alternatively, thepresent invention may be applied to a system which employs a spray dryerapparatus (SDA) or dry scrubber for removal of sulfur oxides from theflue gases, as shown in the lower right-hand side of FIG. 1. In thisconfiguration, the SDA or dry scrubber is typically followed (withrespect to a direction of flue gas flow through the system) by aparticulate collection device (PCD), advantageously a fabric filter (FF)or baghouse, an electrostatic precipitator (ESP) or even a wetelectrostatic precipitator (wet ESP).

Additionally, the present invention can be applied to any SCR catalystthat is adversely affected by poisoning with a phosphorus-based compoundsuch as, but not limited to, H₃PO₄, PO or P₂O₅. As such, the presentinvention is not limited to any one type of SCR catalyst, but rather isbroadly applicable to a wide range of SCR catalyst systems. Suitablecatalyst systems for which the present invention is applicable include,but are not limited to, honeycomb, plate or corrugated typeconfigurations.

In one embodiment, the present invention is directed to reducing therate of SCR catalyst deactivation on Powder River Basin (PRB) coalcombustion units. It should be noted that although the present inventionis described in relation to PRB coal, the present invention is notlimited thereto. Rather, the present invention is broadly applicable toany situation where an SCR catalyst is poisoned by one or more gaseousphosphorus compounds.

In one embodiment, phosphorus in PRB coal is suspected to cause rapiddeactivation in staged combustion and other units. This deactivation issuspected to be caused by the gas phase phosphorus released viacarbothermic reduction reaction. In this reaction under oxygen deficientconditions, phosphorus bearing compounds release gas phase phosphorus bythe following reaction:

P₂O₅ (solid phase compounds)+3C(s)→2PO(g)+3CO(g).

This gas phase phosphorus attaches to the active sites within thecatalyst causing the deactivation of the sites for NO_(x) reduction. Asa result of this deactivation the SCR catalyst cannot carry out theNO_(x) reduction process to the same performance level as unusedcatalyst.

In one embodiment, the present invention relates to a system and methodto prevent formation of gas phase phosphorus species in the combustionenvironment thus reducing, mitigating and/or eliminating the rate of SCRdeactivation. In one embodiment, the present invention accomplishes theaforementioned goal by the addition of at least one iron-bearingcompound to the PRB coal prior to combustion.

In another embodiment, the present invention is directed to a system andmethod designed to increase the catalytic activity and/or catalytic lifespan. In this case, the increase in catalytic activity and/or increasein catalytic life span is measured against a standard, or known, rate ofdecline in catalytic activity and/or life for a given a boiler, fossilfuel boiler, kiln, heater, or any other type of device that generates aflue gas or combustion gas containing NO_(x).

In one embodiment, the iron-bearing compounds of the present inventionis any iron compound (e.g., an iron oxide compound) that is able toundergo reduction in the combustion environments common to boilers,furnaces, power plants, etc. In another embodiment, the iron-bearingcompound of the present invention can be a water soluble, or waterinsoluble, iron-bearing compound. Suitable water soluble iron-bearinginorganic compounds include, but are not limited to, iron (II) acetate(e.g., Fe(C₂H₃O₂)₂.4H₂O), iron (II) nitrate (e.g., Fe(NO₃)₂.6H₂O), iron(III) nitrate (e.g., Fe(NO₃)₃.6H₂O or Fe(NO₃)₃.9H₂O), iron (II) sulfate(e.g., FeSO₄.H₂O, FeSO₄.4H₂O, FeSO₄.5H₂O, or FeSO₄.7H₂O), iron (III)sulfate (e.g., Fe₂(SO₄)₃.9H₂O), or mixtures of two or more thereof.Although various hydrated forms of iron-bearing compounds are listedhere, the present invention is not limited to just the hydrated formslisted above. Rather, if possible, any corresponding anhydrous form ofthe above listed iron-bearing compounds can also be utilized inconjunction with the present invention. Given this, when an iron-bearingcompound is mentioned herein it should be interpreted to encompass botha hydrated form or an anhydrous form regardless of whether or not such aformula is given with “bound water.” Suitable water insolubleiron-bearing compounds include but are not limited to, metallic iron,one or more iron oxides, iron carbonate, or mixtures of two or morethereof. Additionally, a wide range of water soluble, or waterinsoluble, organic iron bearing compounds could be utilized inconjunction with the present invention. As will be discussed below, theiron-bearing compound of the present invention can be supplied in anydesirable form including, but not limited to, powderized form, solidform, as an aqueous solution, as an aqueous suspension or emulsion, orany combination of two or more different forms of iron-bearingcompounds. In still another embodiment, where two different forms ofiron-bearing compounds are supplied in conjunction with the presentinvention, the iron-bearing compound supplied via each different formcan be the same or different. In one particular embodiment, theiron-bearing compound is iron (III) oxide (Fe₂O₃), also known as rediron oxide or hematite. In the embodiment where iron (III) oxide isutilized the reactions of interest that occur in the combustion portionof a boiler or furnace are as shown below:

3Fe₂O₃(s)+CO(g)→2Fe₃O₄(s)+CO₂(g)   (1)

Fe₃O₄(s)+CO(g)→3FeO(s)+CO₂(g)   (2).

It should be noted that the Fe₃O₄, also known as black iron oxide ormagnetite, of the first reaction above can also be written moreaccurately as FeO.Fe₂O₃. The FeO or iron (II) oxide, also known asferrous oxide, which is generated due to the reduction of Fe₂O₃ is thenavailable to tie-up, bind and/or sequester any PO gas present in thecombustion zone, or the flue gas, of a boiler, or furnace, prior toarrival at the SCR. This PO gas will then form Fe—P compounds inparticulate phase prior to arrival at the SCR. The particulate will passthrough the catalyst and avoid the catalyst deterioration.

In another embodiment, the present invention can utilize iron (II)carbonate which is converted to the desired iron (II) oxide in thecombustion zone via the reaction shown below:

FeCO₃(s)→FeO(s)+00 ₂(g)   (3).

In still another embodiment, the present invention can utilize acombination of one or more iron-containing compounds and one or morehalide compounds, with the proviso that the halide containing compoundis not an iron halide. Thus, in this embodiment at least oneiron-containing compound is utilized in conjunction with at least onenon-iron halide containing compound. In still another embodiment, the atleast one iron compound has a generic formula of AX, where A is equal toiron and X is either an oxide or carbonate ion, anion, group, and/ormoiety and the at least one halide compound has a generic formula of BYwhere B is any atom, element, or cation except for iron and Y is ahalide selected from chlorine, bromine, fluorine, or iodine.

In one embodiment, suitable halides for use in conjunction with thepresent invention include, but are not limited to, potassium bromide,potassium chloride, potassium fluoride, potassium iodide, sodiumbromide, sodium chloride, sodium fluoride, sodium iodide, calciumbromide, calcium chloride, calcium fluoride, calcium iodide, aluminumbromide, aluminum chloride, aluminum fluoride, aluminum iodide, othermetal halides (e.g., bromides, chlorides, fluorides and/or iodides) withthe proviso that the metal is not iron, or any mixture of two or morethereof. In still another embodiment, any one or more halide compoundsin accordance with the proviso defined above can be used in combinationwith one or more non-halide containing iron compounds (e.g., iron (II)carbonate). In still another embodiment, the present invention utilizesa combination of iron (II) carbonate with calcium bromide to control theamount and/or concentration of phosphorus in a flue gas, or combustiongas while concurrently permitting both the control of mercury compounds,or mercury-containing compounds, in a flue gas, or combustion gas andthe increase in catalytic activity and/or service life. In still yetanother embodiment, the present invention utilizes a combination of iron(II) carbonate with calcium chloride to control the amount and/orconcentration of phosphorus in a flue gas, or combustion gas whileconcurrently permitting both the control of mercury compounds, ormercury-containing compounds, in a flue gas, or combustion gas and theincrease in catalytic activity and/or service life. In still yet anotherembodiment, the present invention utilizes a combination of iron (II)carbonate with either one, or both, of aluminum bromide and/or aluminumchloride to control the amount and/or concentration of phosphorus in aflue gas, or combustion gas while concurrently permitting both thecontrol of mercury compounds, or mercury-containing compounds, in a fluegas, or combustion gas and the increase in catalytic activity and/orservice life. As used herein, mercury compounds, or mercury-containingcompounds, include, but are not limited to, any compound that containseither oxidized mercury, or bound elemental mercury. In still anotherembodiment, the present invention is directed to concurrently permittingthe control of mercury compounds, or mercury-containing compounds, thatcontain primarily, or only, oxidized mercury.

As used herein, any iron compound suitable for use in conjunction withthe present invention can be utilized in a hydrated or non-hydratedform. As such, reference to any iron compound herein by definitionincludes any hydrated forms that exists whether or not specificallymentioned by chemical formula.

As is known in the art, (see, e.g., United States Patent ApplicationPublication No. 2008/0107579 the text of which is hereby incorporated byreference as though fully set forth herein) halide-containing compoundsare utilized to oxidize elemental mercury present in a flue, orcombustion, gas. Due to this oxidation reaction, the halide portion of asuitable halide-containing compound permits elemental mercury to beconverted into a more favorable form for subsequent capture, orsequestration, via one or more suitable environmental controltechnologies (e.g., a wet scrubber or spray dry absorber (SDA), a fluegas desulfurization system (FGD), a powdered activated carbon system(PAC), or a particulate collecting system such as a fabric filter (FF)or a electrostatic precipitator (ESP)). In one instance, as is known inthe art, the addition of one or more suitable halide-containingcompounds also increases the amount of mercury that isparticulate-bound. Given that numerous patents and publishedapplications detail the manner by which suitable halide-containingcompounds permit the increased recovery of mercury from a flue, orcombustion, gas, a detailed discussion hereof is omitted for the sake ofbrevity.

In any of the above embodiments, the suitable one or more iron-bearingcompounds, and if so desired the one or more halide compounds, can beadded to the coal via one or more pulverizers. In still anotherembodiment, the one or more iron-bearing compounds, and if so desiredthe one or more halide compounds, of the present invention can be addedto the combustion zone of a boiler and/or furnace via one or moresuitable supply lines designed to deliver a powderized, solid, aqueoussuspension, suspension, or aqueous solution of the one or moreiron-bearing compounds and/or the one or more halide compounds to thecombustion zone of a furnace and/or boiler. To this end, FIG. 1illustrates several embodiments of suitable design schemes foraccomplishing this result.

Referring to FIG. 1, there is illustrated a schematic representation ofa typical fossil fuel burning facility, generally designated 10, with anSCR system, and which includes a system for practicing the methods ofthe present invention. As shown, boiler 12 is provided for extractingthe heat from the combustion of a fossil fuel, such as coal, throughcombustion with an oxidant, typically air. The heat is transferred to aworking fluid, such as water, to generate steam used to either generatepower via expansion through a turbine generator apparatus (not shown) orfor industrial processes and/or heating.

The raw coal 14 must be crushed to a desired fineness and dried tofacilitate combustion. Raw coal 14 is temporarily stored in a coalbunker 16 and then transferred by means of a gravimetric or volumetricfeeder 18 to one or more coal pulverizers 20. In the embodiment shown inFIG. 1, there are six (6) coal pulverizers, identified as coalpulverizers A-F. As is known to those skilled in the art, each coalpulverizer 20 grinds the coal to a desired fineness (e.g., 70 percentthrough 200 mesh) and as it is ground, hot primary air from primary airfans (not shown) is conveyed into each coal pulverizer 20 to preheat andremove moisture from the coal to desired levels as it is ground. Theprimary air is also used to convey the pulverized coal (PC) out of eachcoal pulverizer 20 and delivers it along a plurality of pulverized coalsupply lines (one such burner line is identified at A in FIG. 1; asingle coal pulverizer 20 may supply coal through 4 to 8 pulverized coalsupply lines) to the burners 22 on the front and rear walls of theboiler 12. Typically, the burners 22 are located in spaced elevations onone or both of the opposed front and rear walls of the boiler 12, or atthe corners of the boiler in installations known as corner-fired ortangentially-fired units (not shown). The present invention can beutilized in conjunction with, but is not limited solely to, single-wallfired, opposed-wall fired and corner- or tangentially-fired units.Typically, a single coal pulverizer 20 only provides coal to a singleelevation of burners 22 on a wall. Thus, in the embodiment shown in FIG.1, the six coal pulverizers A-F supply corresponding burner elevationsA-F. However, as is known to those skilled in the art, other pulverizerand burner configurations are known (e.g., single pulverizers supplyingburners on multiple walls and/or elevations or multiple pulverizerssupplying burners on a single elevation) and the present inventionapplies to any such configurations.

The combustion process begins in the burner zone 24 of the boiler 12'sfurnace 26, releasing heat and creating hot flue gas 28 which isconveyed upwardly to the upper portion 30 of the boiler 12, acrossheating surfaces schematically indicated as rectangles 32. The flue gas28 is then conveyed across the heating surfaces in the pendantconvection pass 34, into the upper portion 36 of the horizontalconvection pass 38. The flue gas 28 is then conveyed through a selectivecatalytic reduction (SCR) apparatus 40 where NO_(x) in the flue gas isreduced, and then through primary and secondary air heater devicesschematically indicated at 42. The air heaters 42 extract additionalheat from the flue gas 28, lowering the temperature of the flue gas, andpreheating the incoming air used for combustion.

As illustrated in FIG. 1, and downstream of the air heaters 42, the fluegas 28 undergoes further treatment for the removal of particulates andsulfur oxides. Two typical configurations of the downstream equipmentemployed to accomplish these tasks are shown on the right-hand side ofFIG. 1. The first equipment configuration in FIG. 1 comprises aparticulate collection device (PCD) schematically indicated at 44, forremoval of particulates from the flue gas 28, and which may comprise inpractice a fabric filter or an electrostatic precipitator. Downstream ofthe PCD 44 there is provided a wet flue gas desulfurization (WFGD)device, also known as a wet scrubber, for removal of sulfur oxides fromthe flue gas 28. The cleaned, scrubbed flue gas may (optionally) beconveyed through a wet ESP 47 for removal of fine particulate or SO₃,and then conveyed to stack 48 for discharge to the atmosphere.

The second equipment configuration in FIG. 1 comprises a spray dryerapparatus (SDA) schematically indicated at 50, also known as a dryscrubber, for removal of sulfur oxides from the flue gas 28. Downstreamof the SDA 50 there is provided a particulate collection device (PCD)44, as described above, for removal of particulates from the flue gas28. The cleaned, scrubbed flue gas is then conveyed to stack 48 fordischarge to the atmosphere.

The third equipment configuration in FIG. 1 comprises a circulating dryscrubber (CDS) schematically indicated at 49, for removal of sulfuroxides from the flue gas 28. Downstream of CDS 49 there is provided aparticulate collection device (PCD) 44 for removal of particulates fromthe flue gas 28. As in the embodiments above, PCD 44 may comprise anysuitable particulate collection device including, but not limited to, afabric filter or an electrostatic precipitator as described above. Thecleaned, scrubbed flue gas is then conveyed to stack 48 for discharge tothe atmosphere.

The fourth equipment configuration in FIG. 1 comprises a firstparticulate removal device in the form of an electrostatic precipitator(ESP) which is schematically indicated at 44. ESP 44 is configured toremove fine particulates from flue gas 28. Downstream of ESP 44 there isprovided a circulating dry scrubber (CDS) schematically indicated at 49,for removal of sulfur oxides from the flue gas 28. Downstream of CDS 49there is provided a second particulate collection device (PCD) 44 forremoval of any remaining particulates from the flue gas 28. As in theembodiments above, PCD 44 may comprise any suitable particulatecollection device including, but not limited to, a fabric filter or anelectrostatic precipitator as described above. The cleaned, scrubbedflue gas is then conveyed to stack 48 for discharge to the atmosphere.In another embodiment, ESP 44 could be interchangeably replaced with afabric filter unit.

The fifth equipment configuration in FIG. 1 comprises a firstparticulate removal device in the form of either a fabric filter or anelectrostatic precipitator (ESP) which is schematically indicated at 44.FF/ESP 44 is configured to remove fine particulates from flue gas 28.Downstream of FF/ESP 44 there is provided a spray dryer apparatus (SDA)schematically indicated at 50, also known as a dry scrubber, for removalof sulfur oxides from the flue gas 28. Downstream of SDA 50 there isprovided a second particulate collection device (PCD) 44 for removal ofany remaining particulates from the flue gas 28. As in the embodimentsabove, PCD 44 may comprise any suitable particulate collection deviceincluding, but not limited to, a fabric filter or an electrostaticprecipitator as described above. The cleaned, scrubbed flue gas is thenconveyed to stack 48 for discharge to the atmosphere.

In order to further reduce NO_(x) emissions, some boilers 12 employstaged combustion wherein only part of the stoichiometric amount of airis provided in the main burner zone 24, with the balance of the air forcombustion, together with any excess air required due to the fact thatno combustion process is 100 percent efficient, is provided above theburner zone 24 via over fire air (OFA) ports 52. If staged combustion isemployed in a boiler 12, due to the reduced air supplied to the burnerzone 24, a reducing atmosphere is created in the lower portion of thefurnace 26, including the hopper region 54.

In accordance with a first embodiment of the present invention, one ormore suitable iron-bearing compounds, and if so desired one or moresuitable halide compounds, are added to the one or more coal pulverizers20 prior to supplying the pulverized coal to the one or more burners 22.The system and apparatus for accomplishing this desired result is alsoshown in FIG. 1, generally designated 100. The system 100 comprises astorage means 120 for temporarily storing the iron-based phosphorusreduction compound, and if so desired the mercury reducing compound,generally designated 110; delivery means 130, 135 for conveying thecompound 110 to a desired location, including valves, seals, etc. asrequired; and control means 150, advantageously microprocessor-basedcontrol means, which are accessed via an operator via human operatorinterface (I/O) station 160, which includes display and data collectionand storage means as required. Although not illustrated individually,the system of the present invention can, in one embodiment, utilizeindependent storage, delivery and control means (in accordance withthose described above) for each individual iron and/or halide compound.In still another embodiment, the system of the present invention cancomprise one set of storage, delivery and control means for the ironcompounds or compounds utilized herein and one set of storage, deliveryand control means (in accordance with those described above) for thehalide compound or compounds utilized herein.

In FIG. 1, the raw coal 14 to which the iron-based phosphorus reducingcompound 110 has been added is referred to as 140. Advantageously, theiron-based phosphorus reducing compound 110 may be provided along withthe raw coal 14 via the feeder 18, which permits close control andmeasurement of the delivery of both raw coal 14 and iron-basedphosphorus reducing compound 110 into the coal pulverizer 20.Alternatively, the iron-based phosphorus reducing compound 110 may beprovided directly into the coal pulverizer 20 and/or directly into oneor more individual burner lines A-F providing the pulverized coal toindividual burners 22, with suitable sealing devices against thepositive pressure within the coal pulverizer 20 or burner lines A-F. Thedelivery means may be slurry-based or pneumatic as required by theparticulars of the iron-based phosphorus reducing compound 110 and theamount and location of introduction into the flue gas 28. Aninterconnected arrangement of control or signal lines 170, 180, 190 and195 interconnect these various devices to provide control signals,iron-based phosphorus reducing compound 110 level signals, andphosphorus level signals in the flue gas 28 (from a sensor 200) topermit the introduction of the iron-based phosphorus reducing compound110 into the flue gas 28 to be controlled by a human operator, orautomatically controlled. However, if a suitable, real-time sensor 200for measuring levels of gaseous phosphorus in the flue gas 28 is notavailable, flue gas samples may instead be taken at the location 200 forlater laboratory analysis via suitable test methods, which may beinductively coupled plasma-mass spectrometry (ICP-MS). Based upon thelaboratory results, a human operator could then use the operatorinterface 160 to manually input a desired set-point into control means150 for the amount of iron-based phosphorus reducing compound 110introduced into the flue gas 28. Provided that subsequent laboratoryanalyses do not indicate any significant variation in gaseous phosphoruslevels in the flue gas 28, there may be no need for real-time, closecontrol of the introduction of iron-based phosphorus reducing compound110. Instead, the amount of iron-based phosphorus reducing compound 110introduced into the flue gas 28 may be simply a function of boiler loador coal feed rate values.

In still yet another embodiment, the present invention utilizes iron(II) oxide. In this embodiment, the need for a reduction reaction tooccur is eliminated and the addition points for the iron (II) oxide ofthis embodiment are therefore broader then previous embodiments. In thiscase, the iron (II) oxide can be added at any suitable pointpost-combustion and pre-SCR in order to tie up, bind and/or sequesterany PO gas present in the flue gas of a boiler, or furnace, prior toarrival at the SCR. In particular, the iron-based phosphorus reductioncompound can be supplied at one or more of the locations G through Qshown in FIG. 1. More particularly, the iron-based phosphorus reductioncompound can also be provided into the flue gas 28 at one or more of thefollowing locations:

-   -   G: into or below the burner zone 24, in one or more of the        front, rear or side walls, via means separate from the burners        22;    -   H: into the furnace 26 at a location above the burner zone 24,        in one or more of the front, rear or side walls;    -   I, J: into the furnace 26 in the vicinity of or via the OFA        ports 52 on one or both of the front or rear walls;    -   K: into the boiler 12 in the pendant convection pass 34;    -   L: into the boiler 12 in the upper portion 36 of the horizontal        convection pass 38;    -   M, N, O, P: into the boiler 12 in the horizontal convection pass        38; and/or    -   Q: into the boiler 12 in the hopper region below the horizontal        convection pass 38.

Given the above, it should be noted that in addition to the introductionof the one or more iron-based phosphorus reduction compounds, theabove-mentioned systems, methods and/or control apparatuses and/ortechnologies can also be utilized to introduce one or more halidecompounds in accordance with the present invention as detailed above.Thus, in one embodiment, the present invention is directed to a systemwhereby both one or more iron-based compounds and one or more halidecompounds are supplied in any manner per the various methods and/orsystems described herein. In another embodiment, each type of compound,or even each separate compound regardless of type, can be suppliedindividually. In still another embodiment, any combination of two ormore compounds regardless of type (i.e., whether an iron-based compoundor a halide compound) can be supplied together so long as the onecompound does not react detrimentally with the other compound.

Furthermore, given the above, the reduced iron, or iron (II) oxide, ofthe present invention is able to remove the gas phase phosphorus in theform of iron-phosphorus alloys upon coming in contact with the over fireair from iron-phosphorus oxide compounds. This significantly reduces theamount and/or concentration of gas phase phosphorus accumulation in anSCR catalyst. Another advantage of the present invention is that throughaddition of iron a significant portion of any phosphorus present will beiron-bound. Iron-bound phosphorus compounds are less leachable therebyminimizing the transfer of phosphorus to an SCR catalyst. Furthermore,phosphorus associated with and/or bound to an iron compound (e.g., aniron oxide) is more stable than phosphorus that is associated withand/or bound to a calcium compound (e.g., calcium oxide). Given this,the present invention is, in one embodiment, directed to the situationwhere a majority of the phosphorus present in the combustion and/or fluestream is sequestered in a suitable iron-phosphorus-oxygen-containingcompound thereby substantially reducing the amount ofcalcium/phosphorus/oxygen-containing compounds that are able to reactwith SO_(x). This in turn substantially reduces the amount of gaseousphosphorus that is produced in the combustion and/or flue gas stream byrestricting the amount of calcium/phosphorus/oxygen-containing compoundsthat are present in the combustion and/or flue gas stream to react withvarious SO_(x) compounds resulting in the unwanted production of gaseousphosphorus compounds, or phosphorus/oxygen compounds, that can lead tothe undesired poisoning of an SCR catalyst.

In still another embodiment, the iron-bearing compound and the halidecompound of the present invention can be added via separate compounds orcan be added via the same compound and can be supplied in any suitablemanner, including the manner detailed in the FIG. 1. Suitableiron-bearing compounds include, but are not limited to, powderized,solid, aqueous (be it an aqueous-based suspension or aqueous-basedemulsion) and/or water soluble or water insoluble forms of iron-bearingcompounds including, but not limited to, metallic iron, one or more ironoxides, iron carbonate, iron (II) acetate (e.g., Fe(C₂H₃O₂)₂.4H₂O), iron(II) nitrate (e.g., Fe(NO₃)₂.6H₂O), iron (III) nitrate (e.g.,Fe(NO₃)₃.6H₂O or Fe(NO₃)₃.9H₂O), iron (II) sulfate (e.g., FeSO₄.H₂O,FeSO₄.4H₂O, FeSO₄.5H₂O, or FeSO₄.7H₂O), iron (III) sulfate (e.g.,Fe₂(SO₄)₃.9H₂O), iron (II) bromide (e.g., FeBr₂), iron (III) bromide(e.g., FeBr₃, Fe₂Br₆, or FeBr₃.6H₂O), iron (II) chloride (e.g., FeCl₂,FeCl₂.2H₂O, or FeCl₂.4H₂O FeBr₂), iron (III) chloride (e.g., FeCl₃,Fe₂Cl₆, FeCl₃.2½H₂O, or FeCl₃.6H₂O), iron (II) iodide (e.g., FeI₂ orFeI₂.4H₂O), iron (III) iodate (e.g., Fe(IO₃)₃), or mixtures of two ormore thereof. Although various hydrated forms of iron-bearing compoundsare listed here, the present invention is not limited to just thehydrated forms listed above. Rather, if possible, any correspondinganhydrous form of the above listed iron-bearing compounds can also beutilized in conjunction with the present invention. Given this, when aniron-bearing compound is mentioned herein it should be interpreted toencompass both a hydrated form or an anhydrous form regardless ofwhether or not such a formula is given with “bound water.” Suitablehalide compounds include, but are not limited to, potassium bromide,potassium chloride, potassium fluoride, potassium iodide, sodiumbromide, sodium chloride, sodium fluoride, sodium iodide, calciumbromide, calcium chloride, calcium fluoride, calcium iodide, aluminumbromide, aluminum chloride, aluminum fluoride, aluminum iodide, othermetal halides (e.g., bromides, chlorides, fluorides and/or iodides) withthe proviso that the metal is not iron, or any mixture of two or morethereof. If an existing skid is used then one or more aqueous reagentscan be pumped via positive displacement pumps from a storage tank to theone or more coal feeders where the reagent is sprayed on the coal as thecoal passes on a feeder belt upstream of the pulverizers. In thisinstance, if so utilized the one or more halide compounds are chosen tobe soluble in water, or an aqueous-based solvent. Suitable halidessoluble halides include, but are not limited to, potassium bromide,potassium chloride, potassium fluoride, potassium iodide, sodiumbromide, sodium chloride, sodium fluoride, sodium iodide, calciumbromide, calcium chloride, calcium iodide, aluminum bromide, aluminumchloride, aluminum iodide, or any mixtures of two or more thereof. Instill another embodiment, other transition metal halides (e.g.,bromides, chlorides, fluorides and/or iodides) that are not iron halidescan be utilized so long as such compounds are, in this embodiment,soluble in water, or an aqueous-based solvent.

In one embodiment, the present invention is advantageous in that it isapplicable to both existing SCRs (retrofits) and new SCRs. Additionally,the present invention can be applied to plants that utilize biomass as afuel source. In one embodiment, implementation of the present inventioncan be accomplished in a cost-effective manner utilizing low costhardware designed to supply the necessary iron compound to a combustionprocess. The present invention also does not affect the current designof boilers and SCRs.

In one embodiment, the amount of iron compound, or compounds, utilizedin conjunction with the present invention varies depending upon thephosphorus content in the coal to be burned. In one embodiment, thepresent invention is directed to a method and system whereby astoichiometric excess one or more iron compounds are supplied to anypoint prior to an SCR. While not wishing to be bound to any one theory,it has been found that by supplying a stoichiometric excess of ironupstream of an SCR, the catalytic activity and/or catalytic lifespan ofan SCR catalyst can be unexpectedly increased. As can be seen from thegraph of FIG. 2, the addition of a stoichiometric excess of one or moreiron-based compounds not only protects the SCR catalyst from poisoningvia various phosphorus compounds but also increases both the catalyticactivity and catalytic lifespan over a period of at least about 2,000operational hours.

Regarding FIG. 2, FIG. 2 is a graph plotting the original expecteddeactivation for a catalyst without the addition of the iron-bearingcompound, or compounds, of the present invention versus the actualdeactivation of a catalyst with the addition of an iron-bearing compoundof the present invention versus the observed deactivation of a catalystwithout the addition of the iron-bearing compound, or compounds, of thepresent invention. The y-axis of the graph of FIG. 2 is catalyticactivity in decimal terms where 0.9 is equivalent to 90 percent activityas measured when compared to unused virgin catalyst as determined usingany suitable method for determining catalytic activity known to those ofskill in the art. The x-axis of the graph of FIG. 2 is the number ofoperational hours that the catalyst in question is exposed to theaverage operational conditions of a 100 MWe coal plant.

Given the above, in one embodiment the present invention achieves eitherone, or both, of an increase in catalytic activity and/or an increase incatalytic lifespan via the use, introduction and/or delivery of one ormore iron-based compounds. In one embodiment, an increase in either one,or both, of catalytic activity and/or catalytic lifespan of at leastabout 10 percent is achieved at an operational time of at least about2,000 hours versus the catalytic activity and/or catalytic lifespan of agiven catalyst when subjected to similar operational conditions but notsubjected to a supply of one or more iron-based compounds as disclosedherein. As would be apparent to those of skill in the art, various knownmethods are available to measure the baseline catalytic activity as wellas the catalytic activity of various catalysts, including SCR catalysts.As such, a detailed discussion herein is omitted for the sake ofbrevity.

In another embodiment, the present invention achieves an increase ineither one, or both, of catalytic activity and/or catalytic lifespan ofat least about 10 percent is achieved at an operational time of about2,000 hours, an increase of at least about 12.5 percent is achieved atan operational time of about 2,000 hours, an increase of at least about15 percent is achieved at an operational time of about 2,000 hours, anincrease of at least about 17.5 percent is achieved at an operationaltime of about 2,000 hours, an increase of at least about 20 percent isachieved at an operational time of about 2,000 hours, an increase of atleast about 22.5 percent is achieved at an operational time of about2,000 hours, an increase of at least about 25 percent is achieved at anoperational time of about 2,000 hours, an increase of at least about27.5 percent is achieved at an operational time of about 2,000 hours, oreven an increase of at least about 30 percent is achieved at anoperational time of about 2,000 hours versus the catalytic activityand/or catalytic lifespan of a given catalyst when subjected to similaroperational conditions but not subjected to a supply of one or moreiron-based compounds as disclosed herein. Here, as well as elsewhere inthe specification and claims, individual numerical values can becombined to form additional and/or non-disclosed ranges.

In still another embodiment, the present invention achieves an increasein either one, or both, of catalytic activity and/or catalytic lifespanof at least about 10 percent is achieved at an operational time of about2,500 hours, an increase of at least about 12.5 percent is achieved atan operational time of about 2,500 hours, an increase of at least about15 percent is achieved at an operational time of about 2,500 hours, anincrease of at least about 17.5 percent is achieved at an operationaltime of about 2,500 hours, an increase of at least about 20 percent isachieved at an operational time of about 2,500 hours, an increase of atleast about 22.5 percent is achieved at an operational time of about2,500 hours, an increase of at least about 25 percent is achieved at anoperational time of about 2,500 hours, an increase of at least about27.5 percent is achieved at an operational time of about 2,500 hours, oreven an increase of at least about 30 percent is achieved at anoperational time of about 2,500 hours versus the catalytic activityand/or catalytic lifespan of a given catalyst when subjected to similaroperational conditions but not subjected to a supply of one or moreiron-based compounds as disclosed herein. Here, as well as elsewhere inthe specification and claims, individual numerical values can becombined to form additional and/or non-disclosed ranges.

In still yet another embodiment, the present invention achieves anincrease in either one, or both, of catalytic activity and/or catalyticlifespan of at least about 10 percent, at least about 12.5 percent, atleast about 15 percent, at least about 17.5 percent, at least about 20percent, at least about 22.5 percent, at least about 25 percent, atleast about 27.5 percent, or even at least about 30 percent is achievedat an operational time of about 3,000 hours versus the catalyticactivity and/or catalytic lifespan of a given catalyst when subjected tosimilar operational conditions but not subjected to a supply of one ormore iron-based compounds as disclosed herein. In still yet anotherembodiment, the present invention achieves an increase in either one, orboth, of catalytic activity and/or catalytic lifespan of at least about10 percent, at least about 12.5 percent, at least about 15 percent, atleast about 17.5 percent, at least about 20 percent, at least about 22.5percent, at least about 25 percent, at least about 27.5 percent, or evenat least about 30 percent is achieved at an operational time of about3,500 hours, about 4,000 hours, about 4,500 hours, about 5,000 hours,about 6,000 hours, about 7,000 hours, about 7,500 hours, about 8,000hours, about 9,000 hours, about 10,000 hours, about 11,000 hours, about12,000 hours, about 13,000 hours, about 14,000 hours, about 15,000hours, or even about 16,000 hours versus the catalytic activity and/orcatalytic lifespan of a given catalyst when subjected to similaroperational conditions but not subjected to a supply of one or moreiron-based compounds as disclosed herein. Here, as well as elsewhere inthe specification and claims, individual numerical values can becombined to form additional and/or non-disclosed ranges.

As is known to those of skill in the art, the phosphorus content of coalcan be determined by various known methods. Thus, in this instance, thepresent invention is not limited to any one range of iron compounds thatare utilized. Instead, an excess stoichiometric ratio is utilized. Inone embodiment, the excess stoichiometric ratio of iron to phosphorus isin the range of about 2.5:1 to about 10:1, or from about 3:1 to about9:1, or from about 3.5:1 to about 8:1, or from about 4:1 to about 7.5:1,or from about 5:1 to about 7:1, or from about 5.5:1 to about 6.5:1, oreven about 6:1. Here, as well as elsewhere in the specification andclaims, individual range values can be combined to form additionaland/or non-disclosed ranges.

In another embodiment, the amount of iron compound, or compounds,utilized in conjunction with the present invention is within a givenrange when the coal utilized is Powder River Basin/Lignite coal. In thisembodiment, the amount of the iron compound, or compounds, to PowderRiver Basin/Lignite coal is expressed as the amount of iron compound, orcompounds, (hereinafter referred to as just “iron” in only thisinstance) in pounds for every 1,000 pounds of coal. In one embodiment,the amount of iron compound, or compounds, utilized is in the range ofabout 5 pounds of “iron” per 1,000 pounds of coal to about 20 pounds of“iron” per 1,000 pounds of coal. In another embodiment, the amount ofiron compound, or compounds, utilized is in the range of about 5.5pounds of “iron” per 1,000 pounds of coal to about 17.5 pounds of “iron”per 1,000 pounds of coal, or from about 6 pounds of “iron” per 1,000pounds of coal to about 15 pounds of “iron” per 1,000 pounds of coal, orfrom about 7 pounds of “iron” per 1,000 pounds of coal to about 12.5pounds of “iron” per 1,000 pounds of coal, or from about 7.5 pounds of“iron” per 1,000 pounds of coal to about 10 pounds of “iron” per 1,000pounds of coal, or even from about 8 pounds of “iron” per 1,000 poundsof coal to about 9 pounds of “iron” per 1,000 pounds of coal. Here, aswell as elsewhere in the specification and claims, individual rangevalues can be combined to form additional and/or non-disclosed ranges.

In another embodiment, where both an iron-based compound and a halidecompound as defined above are utilized, the amount of iron-basedcompound, or compounds, as compared on a weight basis to the amount ofone or more halide compounds is in the range of about 95 weight partsiron based compound, or compounds to about 5 weight parts halidecompound, or compounds. In another embodiment, the weight ratio ofiron-based compound, or compounds, to halide compound, or compounds, isin the range of about 95:5 to about 75:25, or from about 93.5:6.5 toabout 80:20, or from about 92:8 to about 82.5:17.5, or from about 91:9to about 85:15, or even from about 90:10 to about 87.5:12.5. Thus, inone embodiment, the amount of the one or more halide compounds, if soutilized, can be calculated based on any of the above stated iron-basedcompound, or compounds, amounts via the ratios disclosed in thisparagraph. Here, as well as elsewhere in the specification and claims,individual range values can be combined to form additional and/ornon-disclosed ranges.

In another embodiment, the injection rate of the one or more halidecompounds, if so utilized in conjunction with the present invention, forcontrolling mercury in a flue gas, or combustion gas, is based on anon-limiting example of a 100 MWe coal power plant. In this case, theinjection rate for the one or more halide compounds, if in solution, isin the range of about 0.25 gallons per hour to about 10 gallons perhour, or from about 0.5 gallons per hour to about 5 gallons per hour, oreven from about 1 gallon per hour to about 4 gallons per hour. Inanother embodiment, regardless of power plant or combustion plant size,the one or more halide compounds are supplied at any rate to a flue gas,or combustion gas, sufficient to yield a concentration of halide (e.g.,bromide, chloride or iodide) between about 10 ppm to about 200 ppm, orfrom about 25 ppm to about 175 ppm, or from about 50 ppm to about 150ppm. It should be noted that depending upon the emissions controltechnology in place on the device generating the flue gas, or combustiongas, it may be desirable to use a lower halide concentration in order toprevent any type of detrimental effects to such downstream emissionstechnology. In one embodiment of such an instance the concentration ofhalide is between about 10 ppm to about 125 ppm, or from about 25 ppm toabout 100 ppm, or from about 50 ppm to about 75 ppm. Here, as well aselsewhere in the specification and claims, individual range values (evenfrom different embodiments) can be combined to form additional and/ornon-disclosed ranges.

In light of the above, one of skill in the art would recognize that theamount of one or more iron, or iron-based, compounds necessary to supplythe desired amount of iron to a flue gas, or combustion gas, inaccordance with the process of the present invention will vary dependingupon the size of the device generating such flue gas, or combustion gas.The same can be said of the one or more halide compounds. That is, oneof skill in the art would recognize that the amount of one or morehalide compounds necessary to supply the desired amount of halide to aflue gas, or combustion gas, in accordance with the process of thepresent invention will vary depending upon the size of the devicegenerating such flue gas, or combustion gas. Thus, the present inventionis not limited to any specific rate or range of supply.

In another embodiment, for a 100 MWe coal power plant the amount ofhalide solution (25 weight percent solution) supplied to the flue gas,or combustion gas, is in the range of about 0.25 gallons per hour toabout 6 gallons per hour, or from 0.5 gallons per hour to about 5gallons per hour, or even from 1 gallon per hour to about 4 gallons perhour. Here, as well as elsewhere in the specification and claims,individual range values can be combined to form additional and/ornon-disclosed ranges. However, as is noted above, the present inventionis not limited to solely these supply rates. Rather, any supply rate canbe used in order to achieve the desired concentration of halide.

As would be apparent to one of skill in the art, other additionalfactors can impact the amount of iron-based, iron-bearing and/or ironcompounds supplied in connection with the various embodiments of thepresent invention. Such additional factors include, but are not limitedto, the amount and/or type of phosphorus present in the coal, or othercombustible fuel; the size and/or output of the boiler, heater, kiln, orother flue gas-, or combustion gas-, generating device; and the desiredstoichiometric ratio to be achieved; the type and/or manner ofcombustion, the type and/or arrangement of any applicable equipment orstructure.

In another embodiment, the one or more iron compounds and/or the one ormore halide compounds utilized in conjunction with the present inventioncan be of any particle size and/or particle geometry. Suitable particlegeometries include, but are not limited to, spherical, platelet-like,irregular, elliptical, oblong, or a combination of two or more differentparticle geometries. As would be apparent to those of skill in the art,each different compound, or even the same compound, can be supplied inthe form of one or more particle geometries. In one embodiment, the oneor more iron compounds and/or the one or more halide compounds of thepresent invention, if water soluble, can be supplied in solution form,either independently or together so long as the active components to bedelivered to the flue, or combustion, gas do not adversely react. Insuch an instance, a solution concentration of at least about 15 weightpercent of one or more water soluble iron compounds and/or one or morewater soluble halide compounds is utilized. In another embodiment, asolution concentration of at least about 20 weight percent, at leastabout 25 weight percent, at least about 30 weight percent, at leastabout 35 weight percent, at least about 40 weight percent, at leastabout 45 weight percent, or even at least about 50 weight percent ofmore of the one or more water soluble iron compounds and/or the one ormore water soluble halide compounds is utilized in conjunction with thepresent invention. Here, as well as elsewhere in the specification andclaims, individual range values can be combined to form additionaland/or non-disclosed ranges. As would be appreciated by those of skillin the art, the solution concentration of any one or more water solubleiron compounds and/or the one or more water soluble halide compoundsshould not, in one embodiment, exceed the solubility amount,respectively, for the one or more iron compounds and/or the one or morehalide compounds.

In still another embodiment, the one or more iron compounds and/or theone or more halide compounds of the present invention can be supplied ina powdered form, a solution form, an aqueous suspension form, or acombination of two or more thereof. In the case of an aqueoussuspension, the one or more iron compounds and/or the one or more halidecompounds utilized in conjunction with the present invention should havea suitable particle size. Additionally, even absent the desire to placethe one or more iron compounds and/or the one or more halide compoundsof the present invention into an aqueous solution, the one or more ironcompounds and/or the one or more halide compounds should have a suitableparticle size that facilitates a higher degree of reactivity when placedinto contact with a flue, or combustion, gas. In one embodiment, both ofthese conditions can be met, whether individually or in combination, byone or more iron compounds and/or one or more halide compounds where atleast about 95 percent of the particles have a particle size of lessthan about 400 μm (microns), where at least about 95 percent of theparticles have a particle size of less than about 350 μm (microns),where at least about 95 percent of the particles have a particle size ofless than about 300 μm (microns), where at least about 95 percent of theparticles have a particle size of less than about 250 μm (microns),where at least about 95 percent of the particles have a particle size ofless than about 200 μm (microns), or even where at least about 95percent of the particles have a particle size of less than about 175 μm(microns). Here, as well as elsewhere in the specification and claims,individual range values can be combined to form additional and/ornon-disclosed ranges.

Although not limited hereto, a suitable iron compound for use inconjunction with the present invention is iron (II) carbonate availablefrom Prince Agri Products (a subsidiary of Phibro Animal HealthCorporation located in Ridgefield Park, N.J.). This iron (II) carbonateis a powdered compound where at least about 95 percent of its particlesare less than 200 μm (microns) in size. Additionally, the concentrationof iron (II) carbonate in this product is about 80 percent by weightwith substantially all of the remaining 20 weight percent beingnon-reactive in light of the use here. A suitable halide compound foruse, if so desired, in conjunction with the present invention is calciumbromide available from Tetra Chemical (located in The Woodlands, Tex.).

In the instance where one or more aqueous suspensions is/are utilized inconjunction with the present invention, such aqueous suspension(s) canfurther comprise a suitable amount of one or more anti-settling,suspension, thickening or emulsification agents. Suitable anti-settling,suspension, thickening or emulsification agents include, but are notlimited to, sodium polyacrylates, carbomers, acrylates, and inorganicthickening agents. Other suitable anti-settling, suspension, thickeningor emulsification agents are known to those of skill in the art and assuch a discussion herein is omitted for the sake of brevity. In anotherembodiment, a suitable suspension or emulsification can be achieved viaagitation and does not necessarily require the use of one or moreanti-settling, suspension, thickening or emulsification agents. Inanother embodiment, a combination of one or more anti-settling,suspension, thickening or emulsification agents can be utilized incombination with agitation.

In still another embodiment, the one or more iron compounds and/or theone or more halide compounds of the present invention shouldindependently have a purity of at least about 50 weight percent, atleast about 55 weight percent, at least about 60 weight percent, atleast about 65 weight percent, at least about 70 weight percent, atleast about 75 weight percent, at least about 80 weight percent, atleast about 85 weight percent, at least about 90 weight percent, atleast about 95 weight percent, or even at least about 99 weight percentor higher. Here, as well as elsewhere in the specification and claims,individual range values can be combined to form additional and/ornon-disclosed ranges.

As for the portion of the one or more iron compounds that is not “aniron compound,” such impurities should be non-reactive in theenvironments present in conjunction with the present invention.Alternatively, if reactive, such impurities should either be easilycaptured, removed and/or sequestered, or should not add significantly toany further contamination of any catalyst downstream. In still anotherembodiment, the amount of phosphorus-containing compound impurities inany of the one or more iron compounds and/or the one or more halidecompounds that are utilized in conjunction with the present inventionshould independently be less than about 5 weight percent, less thanabout 2.5 weight percent, less than about 1 weight percent, less thanabout 0.5 weight percent, less than about 0.25 weight percent, less thanabout 0.1 weight percent, or even less than about 0.01 weight percent.Here, as well as elsewhere in the specification and claims, individualrange values can be combined to form additional and/or non-disclosedranges. In still yet another embodiment, the amount ofphosphorus-containing compound impurities in any of the one or more ironcompounds and/or the one or more halide compounds that are utilized inconjunction with the present invention should be zero. That is, in thisembodiment the one or more iron compounds and/or the one or more halidecompounds that are utilized in conjunction with the present inventionshould independently be free from any phosphorus-containing compounds.

While not wishing to be bound to any one theory, it is believed that thepresent invention exploits various preferential reactions betweenphosphorus compounds, or phosphorus-containing compounds, to sequestervarious phosphorus compounds, or phosphorus-containing compounds thatare detrimental to an increased active, or service, life of an SCRcatalyst. Thus, the reactions discussed herein are to be construed asnon-limiting in that other additional reactions may be occurring in thecombustion and/or flue gas stream.

In another embodiment, the present invention is direct to a system andmethod for the injection of iron carbonate, another suitable ironcompound, or a blend of one or more iron compounds and one or morenon-iron-containing halide compounds with coal in the furnace in orderto replenish the active catalytic sites on the surface of SCR catalystwith Fe active sites while simultaneously achieving mercury oxidation.In one instance, the injection material is a blend of iron carbonate(about 90 percent by weight) and a non-iron-containing halogen compound(e.g., calcium bromide 10 percent by weight). As is known to those ofskill in the art, any iron that is present in coal ash (including butnot limited to PRB coal ash) is not catalytically active as it bonds, oris bonded, with various silicates and/or aluminates in the coalcombustion process. In PRB coal more than 90 percent of total ironoccurs as a bonded mineral meaning that it is mostly trapped in glassysilica and/or alumina compounds during the combustion process therebymaking it unavailable for any other chemical reaction. Thus, the presentinvention, by injecting iron separately, provides “free” iron that,while not wishing to be bound to any one theory, is believed to settleonto and/or be deposited onto the surface of fly ash which makes itavailable for further chemical reactions.

This blended material that contains “free” iron as defined above canthen provide iron for increasing the catalytic activity and/or catalyticlifespan of the DeNO_(x) catalyst while, if so provided, the halogenportion of the one or more halide compounds of the present inventionacts to aid, or achieve, mercury oxidation. While not wishing to bebound to any one theory, is believed that when the fly ash getsdeposited on the surface of SCR catalyst the iron on the surface of flyash or iron deposited on catalyst as a result of the injection processprovides sites onto which ammonia and NO_(x) can react to form N₂ andwater. As the iron is injected continuously at a low rate of injection,any active iron sites that become depleted are replaced by new ironsites at a reasonable rate thereby allowing for the extension and/orincrease of catalytic lifespan and/or catalytic activity when comparedto similar untreated catalyst as explained in detail above. The halogenportion of the halide compound, or compounds, oxidizes elemental mercuryinto its oxidized form and makes it easier for removal by a downstreamwet or dry scrubber, or with PAC injection.

While not wishing to be bound to any one example, data to support thisinvention is supplied from a long-term injection test of iron carbonateat a 100 MWe coal power plant. Before exposure of the catalyst to thecombustion flue gas, the catalyst analysis by XRF technique showednegligible iron present both on the surface and in the bulk of catalyst.After approximately 2,000 hours of operation and injection of FeCO₃ acatalyst sample is obtained and analyzed by XRF. This sample shows 0.35percent Fe on the surface and 0.13 percent Fe in bulk. Previously usedcatalyst (no FeCO₃ injection from the same site) had 0.26 percent Fe onsurface and 0.06 percent Fe in bulk after 11,000 hours of operation.Baseline testing prior to the injection of iron carbonate indicates thatthe SO₃ concentration is less than 1 ppm in flue gas at the outlet ofair heater. After 8,000 plus hours of operation the SO₃ concentration ismeasured at the air heater outlet and is about 2.6 ppm. This proves thatiron injection into the furnace is indeed reaching the SCR. The increasein SO₃ concentration can be related to the presence of iron on catalystsurface, since Fe is also a good catalyst for conversion of SO₂ to SO₃.

As noted above, FIG. 2 illustrates catalyst performance with and withoutiron injection. The upper line plot (the one with the lower case “Xs”)is the originally expected catalyst deactivation curve. This catalyst isexpected to last for about 16,000 hours of operation. The lower plot(diamonds) illustrates the actual performance for this catalyst. Thecatalyst actually lasts for only 6,800 hours of operation due tophosphorus deactivation. The middle line (triangles) illustrates theperformance of a catalyst subjected to at least the iron compoundinjection of the present invention. The catalyst in this example is notnew when it is installed but is regenerated catalyst with 15 percentlower initial activity than virgin catalyst.

Thus, in one embodiment, the present invention provides additional sitesfor the DeNO_(x) reaction by injection of one or more iron-bearingcompounds thereby making it possible to significantly improve the lifeand/or catalytic activity of an SCR catalyst beyond presently accepted,or believed, time spans. When utilized, the one or more halide compoundsof the present invention provide a halogen component that permits forincreased mercury oxidation and makes possible mercury removaldownstream by any suitable technology (e.g., AQCS equipment).

In another embodiment, the present invention seeks to at a minimumcontrol the amount and/or concentration of gas phase selenium and/or thenature of the selenium speciation in at least one of the flue gas or anaqueous environment found in one or more emission control devices (e.g.,a WFGD) via the addition of at least one metal compound at any pointdescribed herein with regard to the aforementioned iron-bearingcompound. In yet another embodiment, the present invention relates to amethod and apparatus for controlling, mitigating and/or reducing theamount and/or concentration of selenium contained in and/or emitted byone or more pieces of emission control equipment for boilers, heaters,kilns, or other flue gas-, or combustion gas-, generating devices (e.g.,those located at power plants, processing plants, etc.) via the additionof at least one metal compound at any point described herein with regardto the aforementioned iron-bearing compound. In still yet anotherembodiment, the present invention relates to method and apparatus forcontrolling the selenium speciation in one, or both, of a gas phase or aaqueous phase by the addition of at least one metal (e.g., an aluminummetal additive, or a transition metal additive such as iron, nickel,zinc, copper or other transition metal) additive upstream of either awet flue gas desulfurization (WFGD) unit and/or a dry flue gasdesulfurization (DFGD) unit (i.e., also known as semi-dry flue gasdesulfurization units which include, but are not limited to, spray dryabsorbers (SDAs), circulating dry scrubbers (CDSs), etc.). Given this,in FIG. 1 when the “term” SDA is utilized it should be viewed asencompassing all types DFGD units.

In another embodiment, the present invention seeks to at a minimumcontrol the amount and/or concentration of gas phase selenium and/or thenature of the selenium speciation in at least one of an amine-based postcombustion CO₂ capture processes. In various amine-based post combustionCO₂ capture processes the amine utilized therein will start to degradedue to being subjected to SO₂, CO₂, heat, O₂, and other degradationproducts. Due to the large amine volume, or inventory, needed for a postcombustion CO₂ capture process, the amine degradation volume is verylarge and requires the amine to be regenerated to make operation moreeconomical. This is generally done via a thermal reclaimer, whichcreates a large volume of thermal sludge and/or waste product. It hasbeen observed that the selenium, due to the recirculation process,present in the inlet gas is removed by the process in the thermal sludgeof the thermal reclaimer (this will happen for all amines with thermalreclaiming). Due to the nature of the thermal reclamation process, itconcentrates the removed products from the circulating solution such asselenium. This makes the thermal sludge a hazardous waste and is anadditional problem to be resolved when these processes arecommercialized. When selenium is discovered in a waste stream, the postcombustion CO₂ capture process may be required to shut down until theselenium issue is resolved. By tying up the selenium upstream of thepost combustion CO₂ capture process via the addition of one or moremetal additives of the present invention, this permits allow thecontinued operation of CO₂ capture processes without concern ofconcentrated selenium-containing wastes.

Suitable metal compounds include water soluble or water insolublecompounds, be they inorganic or organic compounds, of iron, aluminum,nickel, zinc, copper, or mixtures of two or more thereof. Suitableiron-bearing compounds include, but are not limited to, powderized,solid, aqueous (be it an aqueous-based suspension or aqueous-basedemulsion) and/or water soluble forms of iron-bearing compoundsincluding, but not limited to, metallic iron, one or more iron oxides,iron carbonate, iron (II) acetate (e.g., Fe(C₂H₃O₂)₂.4H₂O), iron (II)nitrate (e.g., Fe(NO₃)₂.61H₂O), iron (III) nitrate (e.g., Fe(NO₃)₃.6H₂Oor Fe(NO₃)₃.9H₂O), iron (II) sulfate (e.g., FeSO₄.H₂O, FeSO₄.4H₂O,FeSO₄.5H₂O or FeSO₄.7H₂O), iron (III) sulfate (e.g., Fe₂(SO₄)₃.9H₂O),iron (II) bromide (e.g., FeBr₂), iron (III) bromide (e.g., FeBr₃, Fe₂Br₆or FeBr₃.6H₂O), iron (II) chloride (e.g., FeCl₂, FeCl₂.2H₂O orFeCl₂.4H₂O FeBr₂), iron (III) chloride (e.g., FeCl₃, Fe₂Cl₆, FeCl₃.2½H₂Oor FeCl₃.6H₂O), iron (II) iodide (e.g., FeI₂ or FeI₂.4H₂O), iron (III)iodate (e.g., Fe(IO₃)₃), or mixtures of two or more thereof. Suitablealuminum-bearing compounds include, but are not limited to, powderized,solid, aqueous (be it an aqueous-based suspension or aqueous-basedemulsion) and/or water soluble or water insoluble forms ofaluminum-bearing compounds including, but not limited to, metallicaluminum, aluminum acetate (e.g., Al(C₂H₃O₂)₃), aluminum bromate (e.g.,Al(BrO₃)₃.9H₂O), aluminum bromide (e.g., AlBr₃, Al₂Br₆, AlBr₃.6H₂O orAlBr₃.15H₂O), aluminum chloride (e.g., AlCl₃, Al₂Cl₆ or AlCl₃.6H₂O),aluminum fluoride (e.g., AlF₃, AlF₃.3½H₂O or AlF₃.H₂O), aluminumhydroxide (e.g., Al(OH)₂), aluminum iodide (e.g., AlI₃, Al₂I₆ orAlI₃.6H₂O), aluminum nitrate (e.g., Al(NO₃)₃.9H₂O), aluminum oxide(e.g., Al₂O₃, Al₂O₃.H₂ 0 or Al₂O₃.3H₂O), aluminum sulfate (e.g., Al₂(50₄)₃ or Al₂(SO₄)₃.18H₂O), or mixtures of two or more thereof. Suitablenickel-bearing compounds include, but are not limited to, powderized,solid, aqueous (be it an aqueous-based suspension or aqueous-basedemulsion) and/or water soluble or water insoluble forms ofnickel-bearing compounds including, but not limited to, metallic nickel,nickel acetate (e.g., Ni(C₂H₃O₂)₂ or Ni(C₂H₃O₂)₂.4H₂O), nickel bromate(e.g., Ni(BrO₃)₂.6H₂O), nickel bromide (e.g., NiBr₂ or NiBr₂.3H₂O),nickel carbonate or basic nickel carbonate (e.g., NiCO₃,2NiCO₃.3Ni(OH)₂.4H₂O or zaratite), nickel chloride (e.g., NiCl₂ orNiCl₂.6H₂O), nickel fluoride (e.g., NiF₂), nickel hydroxide (e.g.,Ni(OH)₂ or Ni(OH)₂.XH₂O), nickel iodate (e.g., Ni(IO₃)₂ orNi(IO₃)₂.4H₂O), nickel iodide (e.g., Nil₂), nickel nitrate (e.g.,Ni(NO₃)₂.6H₂O), nickel oxide (e.g., NiO), nickel sulfate (e.g., NiSO₄,NiSO₄.7H₂O or NiSO₄.6H₂O), or mixtures of two or more thereof.

Suitable copper-bearing compounds include, but are not limited to,powderized, solid, aqueous (be it an aqueous-based suspension oraqueous-based emulsion) and/or water soluble or water insoluble forms ofcopper-bearing compounds including, but not limited to, metallic copper,copper acetate (e.g., Cu(C₂H₃O₂)₂.CuO.6H₂O or Cu(C₂H₃O₂)₂.H₂O), copperbromate (e.g., Cu(BrO₃)₂.6H₂O), copper bromide (e.g., CuBr, Cu₂Br₂ orCuBr₂), copper trioxybromide (e.g., CuBr₂.3Cu(OH)₂), copper carbonate orbasic copper carbonate (e.g., Cu₂CO₃, CuCO₃.Cu(OH)₂ or 2CuCO₃.Cu(OH)₂),copper chloride (e.g., CuCl, Cu₂Cl₂, CuCl₂ or CuCl₂.2H₂O), copperfluoride (e.g., CuF, Cu₂F₂, CuF₂ or CuF₂.2H₂O), copper hydroxide (e.g.,Cu(OH)₂), copper iodate (e.g., Cu(IO₃)₂ or Cu₃(IO₃)₆.2H₂O), copperiodide (e.g., CuI or Cu₂I₂), copper nitrate (e.g., Cu(NO₃)₂.H₂O orCu(NO₃)₂.3H₂O), copper oxide (e.g., Cu₂O, CuO, CuO₂.H₂O or Cu₄O), coppersulfate (e.g., Cu₂SO₄, CuSO₄ or CuSO₄.5H₂O), or mixtures of two or morethereof. Suitable zinc-bearing compounds include, but are not limitedto, powderized, solid, aqueous (be it an aqueous-based suspension oraqueous-based emulsion) and/or water soluble or water insoluble forms ofzinc-bearing compounds including, but not limited to, metallic zinc,zinc acetate (e.g., Zn(C₂H₃O₂)₂ or Zn(C₂H₃O₂)₂.2H₂O), zinc bromate(e.g., Zn(BrO₃)₂.6H₂O), zinc bromide (e.g., ZnBr₂), zinc carbonate(e.g., ZnCO₃), zinc chloride (e.g., ZnCl₂), zinc ferrate (e.g.,ZnFe₂O₄), zinc fluoride (e.g., ZnF₂ or ZnF₂.4H₂O), zinc hydroxide (e.g.,Zn(OH)₂), zinc iodate (e.g., Zn(IO₃)₂ or Zn(IO₃)₂.2H₂O), zinc iodide(e.g., ZnI₂), zinc nitrate (e.g., Zn(NO₃)₂.3H₂O or Zn(NO₃)₂.6H₂O), zincoxide (e.g., ZnO or ZnO₂.2½H₂O), zinc sulfate (e.g., ZnSO₄, ZnSO₄.6H₂Oor ZnSO₄.7H₂O), or mixtures of two or more thereof.

It should be noted that although various hydrated forms of metal-bearingcompounds are listed here, the present invention is not limited to justthe hydrated forms listed above. Rather, if possible, any correspondinganhydrous form of the above listed metal-bearing compounds can also beutilized in conjunction with the present invention. Given this, when ametal-bearing compound is mentioned herein it should be interpreted toencompass both a hydrated form or an anhydrous form regardless ofwhether or not such a formula is given with “bound water.”

In still another embodiment, the present invention can entail the use ofat least one kaolin-bearing compound to control gas phase sodium andpotassium compounds as described in U.S. Pat. No. 8,303,919 the completedisclosure and teachings of which are hereby incorporated herein byreference in their entirety.

Given the above, the present invention is, in one embodiment, directedto a method and/or apparatus that enables one to control either one, orboth, of gas phase selenium or aqueous selenium in one or more emissioncontrol devices/equipment for boilers, heaters, kilns, or other fluegas-, or combustion gas-, generating devices. While not wishing to bebound to any one theory, it is believed that the addition of the one ormore metal-bearing compounds permits the gas phase and/or aqueous phasecapture of selenium via modification of the selenium speciation therebyresulting in a selenium compound having a lower solubility in water, orother aqueous solutions, than would otherwise occur without the additionof the one or more metal-bearing compounds of the present invention. Asnoted above, the present invention is application to both WFGD and DFGDsystems and permits the control, mitigation, and/or reduction ofselenium in, for example, the effluent of a WFGD, the slurry solution ofa WFGD, the particulate matter resulting from a DFGD, etc. While notwishing to be bound to any one theory, in one embodiment the presentinvention achieves a modification of the selenium speciation in a gasphase and/or a liquid/aqueous phase to an oxidation state and/orselenium compound (e.g., including, but not limited to, an insolubleselenite compound and/or an insoluble selenide compound, etc.) having alow solubility (herein defined as a solubility of less than about 0.1grams per 100 mL, less than about 0.01 grams per 100 mL, less than about0.001 grams per 100 mL, less than about 0.0001 grams per 100 mL, lessthan about 1×10⁻⁵ grams per 100 mL, or less than about 1×10⁻⁶ grams per100 mL in water at SATP); essentially no solubility (herein defined as asolubility of less than about 1×10⁻⁷ grams per 100 mL, less than about1×10⁻⁸ grams per 100 mL, or even less than about 1×10⁻⁹ grams per 100 mLin water at SATP); or even practically zero solubility in water or anaqueous solution (herein defined as a solubility of less than about1×10⁻¹⁰ grams per 100 mL, or less than about 1×10⁻¹¹ grams per 100 mL,or less than about 1×10⁻¹² grams per 100 mL, less than about 1×10⁻¹³grams per 100 mL, or less than about 1×10⁻¹⁴ grams per 100 mL, or lessthan about 1×10⁻¹⁵ grams per 100 mL, or even less than about 1×10⁻¹⁶grams per 100 mL in water at SATP), results in a lower amount and/orconcentration of selenium that is able to be “emitted” and/or “leached”into a surrounding environment (e.g., a river, a lake, groundwater,etc.). As defined herein, SATP is known as “standard ambient temperatureand pressure” and is defined herein to be equivalent to a temperature of298.15 K (i.e., 25° C. or 77° F.) and an absolute pressure of 100 kPa(i.e., 14.504 psi or 0.986 atm). Here, as well as elsewhere in thespecification and claims, individual numerical values can be combined toform additional and/or non-disclosed ranges.

In still yet another embodiment, the present invention's seleniumcontrol can be accomplished with, or without, one or more of: (i) thecontrol of mercury in the flue gas via mercury oxidation and captureusing any suitable mercury control technology discussed herein; (ii) thecontrol of one or more of gas phase sodium and/or gas phase sodiumcompounds; and/or (iii) the control of one or more of gas phasepotassium and/or gas phase potassium compounds. In still yet anotherembodiment, the present invention utilizes at least one iron-bearingcompound to simultaneously control gas phase phosphorus and gas phaseand/or aqueous selenium as described above. In this additionalembodiment of the present invention the amount of iron-bearing compoundthat is supplied in any manner and at any position discussed previouslycan be the same amount discussed above with regard to the control of gasphase phosphorus. In another embodiment, the amount of iron-bearingcompound, or other metal-bearing compound, supplied in accordance withthis embodiment of the present invention is not limited to any oneamount.

In one embodiment, as is known to those of skill in the art upondetermining the selenium content of the coal to be combusted via anysuitable known method, an excess stoichiometric ratio can be utilized.In one embodiment, the excess stoichiometric ratio of metal (e.g., iron,aluminum, nickel, zinc and/or copper via the one or more metal-bearingcompounds) to selenium is in the range of about 2.5:1 to about 10:1, orfrom about 3:1 to about 9:1, or from about 3.5:1 to about 8:1, or fromabout 4:1 to about 7.5:1, or from about 5:1 to about 7:1, or from about5.5:1 to about 6.5:1, or even about 6:1. Here, as well as elsewhere inthe specification and claims, individual range values can be combined toform additional and/or non-disclosed ranges. It should be appreciatedthat in those embodiments of the present invention where an iron-bearingcompound is utilized, it may not be necessary to add any additionaliron-bearing compound in order to control, reduce, and/or mitigate theamount of undesirable selenium species and/or selenium compounds in aflue gas and/or water/aqueous solution as the amount of excessiron-bearing compound utilized for controlling the aforementioned gasphase phosphorus can, in some embodiments, be sufficient to control thenature of the selenium speciation.

In still another embodiment, the present invention relates to methodand/or apparatus that enables, permits and/or achieves a reduction inthe halogen levels necessary to affect mercury capture via one or morehalogen-based mercury oxidation processes. This embodiment of thepresent invention can be accomplished alone, or in combination, with anyof the other embodiments of the present invention that are discussedabove.

As discussed above, in, for example, a coal combustion process theaddition of one or more halogens, or halogen-containing compounds,(e.g., calcium bromide, or any other suitable bromine-containingcompound) forms gaseous hydrogen halide compounds (e.g., HBr, HCl, HF,and/or Hl). Gaseous hydrogen halide compounds including, but not limitedto, HBr gas are not very reactive towards mercury and cause both hightemperature corrosion under reducing atmosphere in a furnace and lowtemperature corrosion at an air heater outlet. For example, HBr isconverted to Br and Br₂ gas by the Deacon reaction shown below:

4HBr(g)+O₂(g)→2H₂O(g)+2Br₂(g).

Br₂, or another elemental form of a different halogen, in the gas phasethen reacts with Hg in the gas phase to produce, for example, mercuricbromide (HgBr₂) in the gas phase. Mercuric bromide is the compound inthis example that contains the oxidized mercury. This form of mercury iseasily removed using flue gas desulfurization (FGD) equipment.Additionally, other coal-based process such as the production of syngasfrom coal produce undesirable levels of phosphorus compounds therebyresulting in the undesirable deactivation of one or more catalystsassociated with such production processes.

In light of the above, it has been unexpectedly discovered that theaddition of at least one metal compound to a combustion gas, or fluegas, stream results in a reduction in the halogen levels necessary toaffect gas-phase mercury control. In other words, the use of at leastone metal-bearing compound according to the present invention has beenunexpectedly discovered to catalyze, facilitate, or increase the amountand/or concentration of the one or more halogen-containing compounds(e.g., calcium bromide, etc.) that are converted from their injectedcompound form through such compound's corresponding hydrogen halide form(e.g., HBr, HCl, HF, and/or Hl) to the corresponding molecular halogenform (Br₂, Cl₂, F₂, and/or I₂).

In another embodiment the present invention can utilize a combination ofone or more metal compounds and one or more halide-containing compounds,with the proviso that the halide containing compound is not a metalhalide. Thus, in this embodiment at least one metal compound, ormetal-bearing, compound is utilized in conjunction with at least onenon-metal halide containing compound. In still another embodiment, theat least one metal, or metal-bearing, compound has a generic formula ofAX, where A is equal to a suitable transition metal (e.g., iron,aluminum, nickel, copper, and/or zinc) and X is either an oxide orcarbonate ion, anion, group, and/or moiety and the at least onehalide-containing compound has a generic formula of BY where B is anyatom, element, or cation except for a transition metal and Y is a halideselected from chlorine, bromine, fluorine, or iodine.

As discussed above, in various coal combustion processes the injectionof one or more halogen-containing compounds is one method that can beutilized for mercury control via a mercury capture process based on suchone or more halogen-containing compounds. However, one drawback toachieving mercury capture and/or reduction via the use of such one ormore halogen-containing compounds is the level of the one or morehalogen-containing compounds necessary to accomplish a desired reductionlevel in the mercury concentration in a coal combustion flue gas. Thenecessary levels of the one or more halogen-containing compoundsrequired to achieve the desired level of mercury capture can lead to theformation of undesirable levels of one or more halogen compounds such ashydrogen halides (e.g., HBr, HCl, HF, and/or Hl) in order to haveavailable a suitable concentration of one or more hydrogen halidecompounds to be converted via, for example, a corresponding Deaconreaction such as the one above or another reaction that convertshydrogen halides to a corresponding molecular form of a halogen, intoone or more corresponding molecular halogens (Br₂, Cl₂, F₂, and/or I₂).As is known by those of skill in the art, having a undesirable level ofone or more hydrogen halide compounds in combustion, or flue, gas canlead to undesirable corrosion, acid rain (if such acid gases are emittedto the atmosphere), destruction or deactivation of downstream emissioncontrol equipment, poisoning or increased wear of one or more downstreamcatalyst compounds (e.g., one or more SCR catalysts), etc. As notedabove, it is such molecular halogen compounds that affect the mercurycapture by oxidizing the mercury in the combustion, or flue, gas fromelemental mercury)(Hg° to ionic mercury (e.g., Hg²⁺) and then capturingthe ionic mercury in a corresponding mercury halide compound (e.g.,HgBr₂).

As noted above, in one embodiment the present invention through the useof one or more metal, or metal-bearing, compounds achieves a reductionin the amount, level, or concentration of one or more halogen-containingcompounds that are injected to affect mercury capture. In oneembodiment, the present invention achieves a reduction of about 20percent by weight or by volume of the amount of one or morehalogen-containing compounds necessary to achieve the same level ofmercury capture through the use of one or more metal, or metal-bearing,compounds as compared to the amount of one or more halogen-containingcompounds necessary without the use of the present invention's one ormore metal, or metal-bearing, compounds. It should be noted that in thisembodiment the one or more metal, or metal-bearing, compounds can beinjected at any of the injection points detailed above. In still anotherembodiment, the present invention through the use of one or more metal,or metal-bearing, compounds achieves a reduction of at least about 25percent, at least about 30 percent, at least about 35 percent, at leastabout 40 percent, at least about 45 percent, at least about 50 percent,at least about 55 percent, or even a reduction of about 60 percent, byweight or by volume, as compared to the amount of one or morehalogen-containing compounds necessary without the use of the presentinvention's one or more metal, or metal-bearing, compounds. Here, aswell as elsewhere in the specification and claims, individual numericalvalues can be combined to form additional and/or non-disclosed ranges.

Given the above, it should be noted that when numerical values areutilized herein with regard to an amount of a reduction that is achievedby one or more embodiments of the present invention, if such numericalvalues are stated in percentages these numerical values and/or rangesencompass separately both reductions measured in terms of weight and interms of volume. Additionally, with regard to the terms of “amount” and“concentration,” the term “amount” is a broad term that is defined in anon-limiting manner to mean “a quantity of something, typically thetotal of a thing or things in number, size, value, or extent,” while“concentration” is a slightly more specific term that is defined in anon-limiting manner to mean “the amount of a specified substance in aunit amount of another substance.” Given these definitions, as usedherein the term “amount” encompasses the definition of the term“concentration” for the purposes of the various embodiments of thepresent invention where a reduction in the amount of something is eitherdiscussed and/or claimed

In another embodiment, the present invention through the use of one ormore metal, or metal-bearing, compounds achieves a reduction of betweenabout 20 percent to about 60 percent, between about 25 percent to about55 percent, between about 30 percent to about 50 percent, or even areduction of between about 35 percent 45 percent, by weight or byvolume, as compared to the amount of one or more halogen-containingcompounds necessary without the use of the present invention's one ormore metal, or metal-bearing, compounds. Here, as well as elsewhere inthe specification and claims, individual numerical values can becombined to form additional and/or non-disclosed ranges.

In one specific instance it was shown that a 50 weight percent reductionin the amount of calcium bromide necessary to achieve a given level ofmercury capture in a coal combustion process (e.g., a low sulfur coalsuch as, but not limited to, Powder River Basin coal) can be achieved byusing, or injection, one or more metal, or metal-bearing, compoundsaccording to the present invention as compared to the amount of calciumbromide necessary to achieve the same level of mercury capture withoutthe use, or injection, of one or more metal, or metal-bearing, compoundsaccording to the present invention. Such a reduction in the amount ofhalogen-containing compound necessary for mercury capture will resultnot only in a reduction in the cost of mercury emission control but alsoa reduction in the one or more undesirable downstream effect caused bythe presence of an undesirable amount and/or concentration of one ormore gaseous hydrogen halide compounds (e.g., HBr, HCl, HF, and/or Hl).

Any suitable amount of the one or more metal, or metal-bearing,compounds of the present invention can be utilized in order to achievethe desired reduction in the amount and/or concentration of the one ormore halogen-containing compounds necessary for mercury capture. Giventhis, this embodiment of the present invention is not limited to theinjection of any one amount and/or concentration, or range of amountsand/or concentrations, of the one or more metal, or metal-bearing,compounds of the present invention. Rather, the amount and/orconcentration of the one or more metal, or metal-bearing, compoundsnecessary to achieve the desired reduction in the amount and/orconcentration of the one or more halogen-containing compounds needed toachieve the desired level of mercury capture will vary based on numberof factors known to those of skill in the art. Such factors include, butare not limited to, the mercury level in the fuel (e.g., coal) to becombusted, the amount of fuel being burned in a given time period, thesize of the plant burning the fuel (e.g., the generation capacity, thenumber of burners, etc.), etc. Some non-limiting examples of the amountsand/or concentrations of the one or more metal, or metal-bearing,compounds that are used in conjunction with this embodiment of thepresent invention are discussed above with regard to other embodimentsof the present invention.

In another embodiment, the one or more metal, or metal-bearing,compounds of the present invention can be utilized for the cleanup ofsyngas produced from fossil fuel gasification, and in particular coalgasification. Syngas contains undesirable amounts, levels, orconcentrations of gaseous phosphine (PH₃). The phosphine in coal-basedsyngas is a catalyst poison for the one or more Fischer-Tropschcatalysts which are used in the process of making many useful chemicalsfrom coal-, or biomass-, produced syngas. Given this, the injection,addition, and/or use of one or more metal, or metal-bearing, compoundsaccording to the present invention in a syngas production process willresult in a reduction in the amount and/or concentration ofphosphorus-containing compounds (e.g., phosphine) present in theresulting syngas. This in turn will result in a reduction in the amount,or level, of poisoning that may result in a Fischer-Tropsch catalystthat is used in conjunction with syngas from coal, biomass and/ornatural gas to produce one or more valuable synthetic lubrication oilsand/or synthetic fuels.

In one embodiment, the present invention achieves a reduction of about20 percent by weight or by volume of the amount of one or more gaseousphosphorus compounds in a syngas production process through the use ofone or more metal, or metal-bearing, compounds as compared to the amountof one or more gaseous phosphorus compounds present in a syngasproduction process that does not utilize the present invention's one ormore metal, or metal-bearing, compounds. It should be noted that in thisembodiment the one or more metal, or metal-bearing, compounds can beinjected at any suitable injection point in the syngas processincluding, but not limited to, the syngas reactor, the syngas cooler,etc. In still another embodiment, the present invention through the useof one or more metal, or metal-bearing, compounds achieves a reductionof at least about 25 percent, at least about 30 percent, at least about35 percent, at least about 40 percent, at least about 45 percent, atleast about 50 percent, at least about 55 percent, at least about 60percent, at least about 65 percent, at least about 70 percent, at leastabout 75 percent, or even a reduction of at least about 80 percent, byweight or by volume, as compared to the amount of one or more gaseousphosphorus compounds present in a syngas production process that doesnot utilize the present invention's one or more metal, or metal-bearing,compounds. Here, as well as elsewhere in the specification and claims,individual numerical values can be combined to form additional and/ornon-disclosed ranges.

In another embodiment, the present invention through the use of one ormore metal, or metal-bearing, compounds achieves a reduction of betweenabout 20 percent to about 80 percent, between about 25 percent to about75 percent, between about 30 percent to about 70 percent, between about35 percent to about 65 percent, between about 40 percent to about 60percent, or even a reduction of between about 45 percent 55 percent, byweight or by volume, as compared to the amount of one or more gaseousphosphorus compounds present in a syngas production process that doesnot utilize the present invention's one or more metal, or metal-bearing,compounds. Here, as well as elsewhere in the specification and claims,individual numerical values can be combined to form additional and/ornon-disclosed ranges.

In still another embodiment, the present invention is directed to theuse of one or more metal, or metal-bearing, compounds in order toachieve a reduction in the concentration, or level, of one or moregaseous acid compounds (e.g., HBr, HCl, HF, Hl, H₃PO₄, etc.) that arepresent in a combustion, or flue, gas. As noted above, an undesirableamount, or concentration, of one or more gaseous acid compounds, orgaseous acid precursor compounds, can: (i) result in corrosion damage(e.g., to one or more downstream conduits, pieces of emission controlequipment, etc.); (ii) result in the emission of a flue gas that resultsin the undesirable formation of acid rain due to the amount and/orconcentration of the one or more gaseous acid compounds containedtherein; (iii) result in the poisoning of any activated carbon materialthat is injected for mercury control; and/or (iv) result in thepoisoning of any one or more downstream catalysts (e.g., a downstreamSCR catalyst, etc.)

Given the above, suitable metal, or metal-bearing, compounds for use inthe halogen reduction embodiments, the syngas embodiments and/or theacid gas control embodiments of the present invention include watersoluble or water insoluble compounds, be they inorganic or organiccompounds, of iron, nickel, zinc, copper, or mixtures of two or morethereof. Suitable iron-bearing compounds include, but are not limitedto, powderized, solid, aqueous (be it an aqueous-based suspension oraqueous-based emulsion) and/or water soluble forms of iron-bearingcompounds including, but not limited to, metallic iron, one or more ironoxides, iron carbonate, iron (II) acetate (e.g., Fe(C₂H₃O₂)₂.4H₂O), iron(II) nitrate (e.g., Fe(NO₃)₂.6H₂O), iron (III) nitrate (e.g.,Fe(NO₃)₃.6H₂O or Fe(NO₃)₃.9H₂O), iron (II) sulfate (e.g., FeSO₄.H₂O,FeSO₄.4H₂O, FeSO₄.5H₂O or FeSO₄.7H₂O), iron (III) sulfate (e.g.,Fe₂(SO₄)₃.9H₂O), iron (II) bromide (e.g., FeBr₂), iron (III) bromide(e.g., FeBr₃, Fe₂Br₆ or FeBr₃.6H₂O), iron (II) chloride (e.g., FeCl₂,FeCl₂.2H₂O or FeCl₂.4H₂O FeBr₂), iron (III) chloride (e.g., FeCl₃,Fe₂Cl₆, FeCl₃.2½H₂O or FeCl₃.6H₂O), iron (II) iodide (e.g., FeI₂ orFeI₂.4H₂O), iron (III) iodate (e.g., Fe(IO₃)₃), or mixtures of two ormore thereof. Suitable nickel-bearing compounds include, but are notlimited to, powderized, solid, aqueous (be it an aqueous-basedsuspension or aqueous-based emulsion) and/or water soluble or waterinsoluble forms of nickel-bearing compounds including, but not limitedto, metallic nickel, nickel acetate (e.g., Ni(C₂H₃O₂)₂ orNi(C₂H₃O₂)₂.4H₂O), nickel bromate (e.g., Ni(BrO₃)₂.6H₂O), nickel bromide(e.g., NiBr₂ or NiBr₂.3H₂O), nickel carbonate or basic nickel carbonate(e.g., NiCO₃, 2NiCO₃.3Ni(OH)₂.4H₂O or zaratite), nickel chloride (e.g.,NiCl₂ or NiCl₂.6H₂O), nickel fluoride (e.g., NiF₂), nickel hydroxide(e.g., Ni(OH)₂ or Ni(OH)₂.XH₂O), nickel iodate (e.g., Ni(IO₃)₂ orNi(IO₃)₂.4H₂O), nickel iodide (e.g., NiI₂), nickel nitrate (e.g.,Ni(NO₃)₂.6H₂O), nickel oxide (e.g., NiO), nickel sulfate (e.g., NiSO₄,NiSO₄.7H₂O or NiSO₄.6H₂O), or mixtures of two or more thereof.

Suitable copper-bearing compounds include, but are not limited to,powderized, solid, aqueous (be it an aqueous-based suspension oraqueous-based emulsion) and/or water soluble or water insoluble forms ofcopper-bearing compounds including, but not limited to, metallic copper,copper acetate (e.g., Cu(C₂H₃O₂)₂.CuO.6H₂O or Cu(C₂H₃O₂)₂.H₂O), copperbromate (e.g., Cu(BrO₃)₂.6H₂O), copper bromide (e.g., CuBr, Cu₂Br₂ orCuBr₂), copper trioxybromide (e.g., CuBr₂.3Cu(OH)₂), copper carbonate orbasic copper carbonate (e.g., Cu₂CO₃, CuCO₃.Cu(OH)₂ or 2CuCO₃.Cu(OH)₂),copper chloride (e.g., CuCl, Cu₂Cl₂, CuCl₂ or CuCl₂.2H₂O), copperfluoride (e.g., CuF, Cu₂F₂, CuF₂ or CuF₂.2H₂O), copper hydroxide (e.g.,Cu(OH)₂), copper iodate (e.g., Cu(IO₃)₂ or Cu₃(IO₃)₆.2H₂O), copperiodide (e.g., CuI or Cu₂I₂), copper nitrate (e.g., Cu(NO₃)₂.H₂O orCu(NO₃)₂.3H₂O), copper oxide (e.g., Cu₂O, CuO, CuO₂.H₂O or Cu₄O), coppersulfate (e.g., Cu₂SO₄, CuSO₄ or CuSO₄.5H₂O), or mixtures of two or morethereof. Suitable zinc-bearing compounds include, but are not limitedto, powderized, solid, aqueous (be it an aqueous-based suspension oraqueous-based emulsion) and/or water soluble or water insoluble forms ofzinc-bearing compounds including, but not limited to, metallic zinc,zinc acetate (e.g., Zn(C₂H₃O₂)₂ or Zn(C₂H₃O₂)₂.2H₂O), zinc bromate(e.g., Zn(BrO₃)₂.6H₂O), zinc bromide (e.g., ZnBr₂), zinc carbonate(e.g., ZnCO₃), zinc chloride (e.g., ZnCl₂), zinc ferrate (e.g.,ZnFe₂O₄), zinc fluoride (e.g., ZnF₂ or ZnF₂.4H₂O), zinc hydroxide (e.g.,Zn(OH)₂), zinc iodate (e.g., Zn(IO₃)₂ or Zn(IO₃)₂.2H₂O), zinc iodide(e.g., ZnI₂), zinc nitrate (e.g., Zn(NO₃)₂.3H₂O or Zn(NO₃)₂.6H₂O), zincoxide (e.g., ZnO or ZnO₂.½H₂O), zinc sulfate (e.g., ZnSO₄, ZnSO₄.6H₂O orZnSO₄.7H₂O), or mixtures of two or more thereof.

It should be noted that although various hydrated forms of metal-bearingcompounds are listed here, the present invention is not limited to justthe hydrated forms listed above. Rather, if possible, any correspondinganhydrous form of the above listed metal-bearing compounds can also beutilized in conjunction with the present invention. Given this, when ametal-bearing compound is mentioned herein it should be interpreted toencompass both a hydrated form or an anhydrous form regardless ofwhether or not such a formula is given with “bound water.”

While specific embodiments of the present invention have been shown anddescribed in detail to illustrate the application and principles of theinvention, it will be understood that it is not intended that thepresent invention be limited thereto and that the invention may beembodied otherwise without departing from such principles. In someembodiments of the invention, certain features of the invention maysometimes be used to advantage without a corresponding use of the otherfeatures. Accordingly, all such changes and embodiments properly fallwithin the scope of the following claims.

What is claimed is:
 1. A method for reducing the amount and/orconcentration of one or more halogen-containing compounds used toachieve mercury capture in a flue gas, the method comprising the stepsof: (a) providing one or more halogen-containing compounds to acombustion zone or flue gas stream of a furnace, or boiler, prior toentry of the flue gas into an SCR, wherein the halogen portion of theone or more halogen-containing compounds are liberated in the combustionzone or flue gas stream of the furnace or boiler and are converted toone or more corresponding gaseous hydrogen halide compounds; (b)providing one or more metal-bearing compounds to a combustion zone orflue gas stream of a furnace, or boiler, at a point that is both priorto entry of the flue gas into an SCR as well as after a point that wherethe majority of the one or more halogen-bearing compounds have beenconverted to the corresponding gaseous hydrogen halides; (c) permittingone or more metal-bearing compounds to catalyze the conversion of thecorresponding one or more hydrogen halides to one or more correspondingelemental halogen compounds; and (d) permitting the resulting one ormore corresponding elemental halogen compounds to react with gaseousmercury present in the combustion zone or flue gas stream of thefurnace, or boiler, thereby resulting in oxidation of the gaseousmercury so as to convert the gaseous mercury into one or morecorresponding mercury halides.
 2. The method of claim 1, wherein themetal-bearing compound is selected from at least one inorganiciron-bearing compound.
 3. The method of claim 1, wherein themetal-bearing compound is selected from metallic iron, one or more ironoxides, iron carbonate, iron (II) acetate, iron (II) nitrate, iron (III)nitrate, iron (II) sulfate, iron (III) sulfate, or mixtures of two ormore thereof.
 4. The method of claim 1, wherein the metal-bearingcompound is selected from iron (III) oxide, iron (II) carbonate, iron(II) oxide, iron (II) acetate, or mixtures of two or more thereof. 5.The method of claim 1, wherein the metal-bearing compound is selectedfrom an organic iron-bearing compound.
 6. The method of claim 1, whereinthe metal-bearing compound is selected from metallic nickel, nickelacetate, nickel bromate, nickel bromide, nickel carbonate, basic nickelcarbonate, nickel chloride, nickel fluoride, nickel hydroxide, nickeliodate, nickel iodide, nickel nitrate, nickel oxide, nickel sulfate, ormixtures of two or more thereof.
 7. The method of claim 1, wherein themetal-bearing compound is selected from an organic nickel-bearingcompound.
 8. The method of claim 1, wherein the metal-bearing compoundis selected from metallic copper, copper acetate, copper bromate, copperbromide, copper trioxybromide, copper carbonate, basic copper carbonate,copper chloride, copper fluoride, copper hydroxide, copper iodate,copper iodide, copper nitrate, copper oxide, copper sulfate, or mixturesof two or more thereof.
 9. The method of claim 1, wherein themetal-bearing compound is selected from an organic copper-bearingcompound.
 10. The method of claim 1, wherein the metal-bearing compoundis selected from metallic zinc, zinc acetate, zinc bromate, zincbromide, zinc carbonate, zinc chloride, zinc ferrate, zinc fluoride,zinc hydroxide, zinc iodate, zinc iodide, zinc nitrate, zinc oxide, zincsulfate, or mixtures of two or more thereof.
 11. The method of claim 1,wherein the metal-bearing compound is selected from an organiczinc-bearing compound.
 12. The method of claim 1, wherein themetal-bearing compound is selected from one or more iron-bearingcompounds, one or more nickel-bearing compounds, one or morecopper-bearing compounds, one or more zinc-bearing compounds, ormixtures of any two or more thereof.
 13. The method of claim 1, whereinthe at least one metal-bearing compound is provided to the combustionzone via addition to pulverized coal.
 14. The method of claim 1, whereinthe at least one metal-bearing compound is provided to the combustionzone via a dedicated supply line.
 15. The method of claim 1, wherein theamount of the one or more halogen compounds necessary to achieve adesired level of mercury capture is reduced by at least 30 percent dueto the implementation of the method of claim 1 when compared to theamount of the one or more halogen compounds necessary to achieve thesame desired level of mercury capture without the implementation of themethod of claim
 1. 16. The method of claim 1, wherein the amount of theone or more halogen compounds necessary to achieve a desired level ofmercury capture is reduced by at least 50 percent due to theimplementation of the method of claim 1 when compared to the amount ofthe one or more halogen compounds necessary to achieve the same desiredlevel of mercury capture without the implementation of the method ofclaim
 1. 17. The method of claim 1, wherein the method further comprisesthe step of controlling one or more of gas phase sodium, gas phasesodium compounds, gas phase potassium, and/or gas phase potassiumcompounds via the additional of at least one kaolin-bearing compound.18. The method of claim 1, wherein the method simultaneously achievesselenium speciation control.
 19. The method of claim 1, wherein the oneor more halogen-containing compounds are selected from one or moreorganic, or inorganic, bromine-containing compounds.
 20. The method ofclaim 1, wherein the one or more halogen-containing compounds areselected from one or more inorganic bromine-containing compounds.
 21. Amethod for reducing the amount and/or concentration of one or moregaseous acid compounds in a flue gas, the method comprising the stepsof: (i) providing at least one fossil fuel, or biomass, to a furnace, orboiler; (ii) combusting the at least one fossil fuel, or biomass,wherein the combustion process produces one or more gaseous acidcompounds; (iii) providing one or more metal-bearing compounds to acombustion zone or flue gas stream of the furnace, or boiler; (iv)permitting one or more metal-bearing compounds to react with the one ormore gaseous acid compounds present in the combustion, or flue, gas inorder to convert the one or more gaseous acid compounds into a lessacidic metal-containing compound.
 22. The method of claim 21, whereinthe metal-bearing compound is selected from at least one inorganiciron-bearing compound.
 23. The method of claim 21, wherein themetal-bearing compound is selected from metallic iron, one or more ironoxides, iron carbonate, iron (II) acetate, iron (II) nitrate, iron (III)nitrate, iron (II) sulfate, iron (III) sulfate, or mixtures of two ormore thereof.
 24. The method of claim 21, wherein the metal-bearingcompound is selected from iron (III) oxide, iron (II) carbonate, iron(II) oxide, iron (II) acetate, or mixtures of two or more thereof. 25.The method of claim 21, wherein the metal-bearing compound is selectedfrom an organic iron-bearing compound.
 26. The method of claim 21,wherein the metal-bearing compound is selected from metallic nickel,nickel acetate, nickel bromate, nickel bromide, nickel carbonate, basicnickel carbonate, nickel chloride, nickel fluoride, nickel hydroxide,nickel iodate, nickel iodide, nickel nitrate, nickel oxide, nickelsulfate, or mixtures of two or more thereof.
 27. The method of claim 21,wherein the metal-bearing compound is selected from an organicnickel-bearing compound.
 28. The method of claim 21, wherein themetal-bearing compound is selected from metallic copper, copper acetate,copper bromate, copper bromide, copper trioxybromide, copper carbonate,basic copper carbonate, copper chloride, copper fluoride, copperhydroxide, copper iodate, copper iodide, copper nitrate, copper oxide,copper sulfate, or mixtures of two or more thereof.
 29. The method ofclaim 21, wherein the metal-bearing compound is selected from an organiccopper-bearing compound.
 30. The method of claim 21, wherein themetal-bearing compound is selected from metallic zinc, zinc acetate,zinc bromate, zinc bromide, zinc carbonate, zinc chloride, zinc ferrate,zinc fluoride, zinc hydroxide, zinc iodate, zinc iodide, zinc nitrate,zinc oxide, zinc sulfate, or mixtures of two or more thereof.
 31. Themethod of claim 21, wherein the metal-bearing compound is selected froman organic zinc-bearing compound.
 32. The method of claim 21, whereinthe metal-bearing compound is selected from one or more iron-bearingcompounds, one or more nickel-bearing compounds, one or morecopper-bearing compounds, one or more zinc-bearing compounds, ormixtures of any two or more thereof.
 33. The method of claim 21, whereinthe at least one metal-bearing compound is provided to the combustionzone via addition to pulverized coal.
 34. The method of claim 21,wherein the at least one metal-bearing compound is provided to thecombustion zone via a dedicated supply line.
 35. The method of claim 21,wherein the one or more gaseous acid compounds in the flue gas that arereduced in amount and/or concentration include one or more of HBr, HCl,HF, Hl, H₃PO₄, or combinations of two or more thereof.
 36. The method ofclaim 21, wherein the resulting reduction in the amount and/orconcentration of the one or more gaseous acid compounds results in areduction in the level of poisoning in any activated carbon materialthat is present in the flue gas.
 37. A method for reducing theconcentration of one or more gaseous phosphorus compounds in a syngasproduction process, the method comprising the steps of: (A) providing atleast one fossil fuel, or biomass, to a syngas reactor; (B) providingone or more metal-bearing compounds to the syngas reactor; (C) reactingthe at least one fossil fuel, or biomass, and the one or moremetal-bearing compounds to produce a syngas, wherein the syngas has areduced level of one or more one or more gaseous phosphorus compounds ascompared to the amount and/or concentration of one or more gaseousphosphorus compounds present in a syngas production process that doesnot utilize the one or more metal-bearing compounds.
 38. The method ofclaim 37, wherein the metal-bearing compound is selected from at leastone inorganic iron-bearing compound.
 39. The method of claim 37, whereinthe metal-bearing compound is selected from metallic iron, one or moreiron oxides, iron carbonate, iron (II) acetate, iron (II) nitrate, iron(III) nitrate, iron (II) sulfate, iron (III) sulfate, or mixtures of twoor more thereof.
 40. The method of claim 37, wherein the metal-bearingcompound is selected from iron (III) oxide, iron (II) carbonate, iron(II) oxide, iron (II) acetate, or mixtures of two or more thereof. 41.The method of claim 37, wherein the metal-bearing compound is selectedfrom an organic iron-bearing compound.
 42. The method of claim 37,wherein the metal-bearing compound is selected from metallic nickel,nickel acetate, nickel bromate, nickel bromide, nickel carbonate, basicnickel carbonate, nickel chloride, nickel fluoride, nickel hydroxide,nickel iodate, nickel iodide, nickel nitrate, nickel oxide, nickelsulfate, or mixtures of two or more thereof.
 43. The method of claim 37,wherein the metal-bearing compound is selected from an organicnickel-bearing compound.
 44. The method of claim 37, wherein themetal-bearing compound is selected from metallic copper, copper acetate,copper bromate, copper bromide, copper trioxybromide, copper carbonate,basic copper carbonate, copper chloride, copper fluoride, copperhydroxide, copper iodate, copper iodide, copper nitrate, copper oxide,copper sulfate, or mixtures of two or more thereof.
 45. The method ofclaim 37, wherein the metal-bearing compound is selected from an organiccopper-bearing compound.
 46. The method of claim 37, wherein themetal-bearing compound is selected from metallic zinc, zinc acetate,zinc bromate, zinc bromide, zinc carbonate, zinc chloride, zinc ferrate,zinc fluoride, zinc hydroxide, zinc iodate, zinc iodide, zinc nitrate,zinc oxide, zinc sulfate, or mixtures of two or more thereof.
 47. Themethod of claim 37, wherein the metal-bearing compound is selected froman organic zinc-bearing compound.
 48. The method of claim 37, whereinthe metal-bearing compound is selected from one or more iron-bearingcompounds, one or more nickel-bearing compounds, one or morecopper-bearing compounds, one or more zinc-bearing compounds, ormixtures of any two or more thereof.
 49. The method of claim 37, whereinthe method achieves a reduction of between about 20 percent to about 80percent in the one or more one or more gaseous phosphorus compounds ascompared to the amount and/or concentration of the one or more gaseousphosphorus compounds present in a syngas production process that doesnot utilize the one or more metal-bearing compounds.
 50. The method ofclaim 37, wherein the method achieves a reduction of between about 25percent to about 75 percent in the one or more one or more gaseousphosphorus compounds as compared to the amount and/or concentration ofthe one or more gaseous phosphorus compounds present in a syngasproduction process that does not utilize the one or more metal-bearingcompounds.
 51. The method of claim 37, wherein the method achieves areduction of at least about 20 percent in the one or more one or moregaseous phosphorus compounds as compared to the amount and/orconcentration of one or more gaseous phosphorus compounds present in asyngas production process that does not utilize the one or moremetal-bearing compounds.
 52. The method of claim 37, wherein the methodachieves a reduction of at least about 30 percent in the one or more oneor more gaseous phosphorus compounds as compared to the amount and/orconcentration of one or more gaseous phosphorus compounds present in asyngas production process that does not utilize the one or moremetal-bearing compounds.
 53. The method of claim 37, wherein the methodachieves a reduction of at least about 50 percent in the one or more oneor more gaseous phosphorus compounds as compared to the amount and/orconcentration of one or more gaseous phosphorus compounds present in asyngas production process that does not utilize the one or moremetal-bearing compounds.
 54. The method of claim 37, wherein the methodachieves a reduction of at least about 80 percent in the one or more oneor more gaseous phosphorus compounds as compared to the amount and/orconcentration of one or more gaseous phosphorus compounds present in asyngas production process that does not utilize the one or moremetal-bearing compounds.